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• How to diagnose frequent segfaults

  - by Andreas Gohr

  My server is logging frequent segmentation faults to /var/log/kern.log in different tools. So far I've seen them in Perl, PHP and rsync. All installed software is up-to-date Debian packages. Here's an exerpt from the log file: Mar 2 01:07:54 gaz kernel: [ 5316.246303] imapsync[4533]: segfault at 8b ip 00007fb448c98fe6 sp 00007ffff571dd68 error 4 in libperl.so.5.10.1[7fb448bd7000+164000] Mar 2 01:17:42 gaz kernel: [ 5904.354307] php5-cgi[4441]: segfault at 2bb3dc8 ip 0000000002bb3dc8 sp 00007fffbeeaae48 error 15 Mar 2 02:54:05 gaz kernel: [11687.922316] php5-cgi[4495]: segfault at 2d7acf9 ip 0000000002d7acf9 sp 00007fff60c6eb18 error 15 Mar 2 10:50:08 gaz kernel: [40250.390322] BUG: unable to handle kernel paging request at 00000000024b03f0 Mar 2 10:50:08 gaz kernel: [40250.390341] IP: [<00000000024b03f0>] 0x24b03f0 Mar 2 10:50:08 gaz kernel: [40250.390353] PGD 208c71067 PUD 21c811067 PMD 209329067 PTE 8000000211c88067 Mar 2 10:50:08 gaz kernel: [40250.390365] Oops: 0011 [#1] SMP Mar 2 10:50:08 gaz kernel: [40250.390373] last sysfs file: /sys/devices/pci0000:00/0000:00:12.0/host4/target4:0:0/4:0:0:0/block/sdb/stat Mar 2 10:50:08 gaz kernel: [40250.390386] CPU 1 Mar 2 10:50:08 gaz kernel: [40250.390392] Modules linked in: cpufreq_userspace cpufreq_stats cpufreq_powersave cpufreq_conservative xt_recent xt_tcpudp iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ ipv4 ip6table_filter ip6_tables xt_DSCP xt_TCPMSS ipt_LOG ipt_REJECT iptable_mangle iptable_filter xt_multiport xt_state xt_limit xt_conntrack nf_conntrack_ftp nf_conntrack ip_tables x_tables loop snd _hda_codec_atihdmi snd_hda_intel snd_hda_codec snd_hwdep snd_pcm radeon snd_timer ttm snd drm_kms_helper soundcore drm snd_page_alloc i2c_algo_bit shpchp i2c_piix4 edac_core pcspkr k8temp evdev edac_m ce_amd pci_hotplug i2c_core button ext3 jbd mbcache dm_mod powernow_k8 aacraid 3w_9xxx 3w_xxxx raid10 raid456 async_raid6_recov async_pq raid6_pq async_xor xor async_memcpy async_tx raid1 raid0 md_mod sata_nv sata_sil sata_via sd_mod crc_t10dif ata_generic ahci pata_atiixp ohci_hcd libata r8169 mii thermal ehci_hcd processor thermal_sys scsi_mod usbcore nls_base [last unloaded: scsi_wait_scan] Mar 2 10:50:08 gaz kernel: [40250.390566] Pid: 11482, comm: munin-limits Not tainted 2.6.32-5-amd64 #1 MS-7368 Mar 2 10:50:08 gaz kernel: [40250.390576] RIP: 0010:[<00000000024b03f0>] [<00000000024b03f0>] 0x24b03f0 Mar 2 10:50:08 gaz kernel: [40250.390586] RSP: 0018:ffff88021cc8dec0 EFLAGS: 00010286 Mar 2 10:50:08 gaz kernel: [40250.390593] RAX: 000000001ddc1000 RBX: 0000000000000010 RCX: ffffffff810f9904 Mar 2 10:50:08 gaz kernel: [40250.390600] RDX: 0000000000000000 RSI: ffffea0007688200 RDI: 0000000000000286 Mar 2 10:50:08 gaz kernel: [40250.390608] RBP: 00000000ffffffea R08: 0000000000000025 R09: 7865542f30312e35 Mar 2 10:50:08 gaz kernel: [40250.390615] R10: 000000d01cc8ddf8 R11: 0000000000000246 R12: ffff88021cc8def8 Mar 2 10:50:08 gaz kernel: [40250.390622] R13: 0000000002295010 R14: 00000000022c9db0 R15: 0000000002488d78 Mar 2 10:50:08 gaz kernel: [40250.390630] FS: 00007f3b3c8b2700(0000) GS:ffff880008d00000(0000) knlGS:0000000000000000 Mar 2 10:50:08 gaz kernel: [40250.390641] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Mar 2 10:50:08 gaz kernel: [40250.390648] CR2: 00000000024b03f0 CR3: 000000021c5d1000 CR4: 00000000000006e0 Mar 2 10:50:08 gaz kernel: [40250.390656] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Mar 2 10:50:08 gaz kernel: [40250.390663] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Mar 2 10:50:08 gaz kernel: [40250.390671] Process munin-limits (pid: 11482, threadinfo ffff88021cc8c000, task ffff88021bf59530) Mar 2 10:50:08 gaz kernel: [40250.390681] Stack: Mar 2 10:50:08 gaz kernel: [40250.390687] ffffffff810f1d4a ffff880208c63228 0000000000000000 00007fffc2dcecc0 Mar 2 10:50:08 gaz kernel: [40250.390697] <0> 00000000024ba2b0 0000000002295010 ffffffff810f1e3d 0000000000000004 Mar 2 10:50:08 gaz kernel: [40250.390712] <0> ffff88021bf59530 ffff88021c4edc00 ffffffff812fe0b6 ffff88021c4edc60 Mar 2 10:50:08 gaz kernel: [40250.390732] Call Trace: Mar 2 10:50:08 gaz kernel: [40250.390742] [<ffffffff810f1d4a>] ? vfs_fstatat+0x2c/0x57 Mar 2 10:50:08 gaz kernel: [40250.390750] [<ffffffff810f1e3d>] ? sys_newstat+0x11/0x30 Mar 2 10:50:08 gaz kernel: [40250.390760] [<ffffffff812fe0b6>] ? do_page_fault+0x2e0/0x2fc Mar 2 10:50:08 gaz kernel: [40250.390768] [<ffffffff812fbf55>] ? page_fault+0x25/0x30 Mar 2 10:50:08 gaz kernel: [40250.390777] [<ffffffff81010b42>] ? system_call_fastpath+0x16/0x1b Mar 2 10:50:08 gaz kernel: [40250.390783] Code: Bad RIP value. Mar 2 10:50:08 gaz kernel: [40250.390791] RIP [<00000000024b03f0>] 0x24b03f0 Mar 2 10:50:08 gaz kernel: [40250.390799] RSP <ffff88021cc8dec0> Mar 2 10:50:08 gaz kernel: [40250.390805] CR2: 00000000024b03f0 Mar 2 10:50:08 gaz kernel: [40250.391051] ---[ end trace 1cc1473b539c7f6e ]--- Mar 2 11:42:20 gaz kernel: [43382.242301] php5-cgi[10963]: segfault at d81160 ip 0000000000d81160 sp 00007fff3adcb058 error 15 Mar 2 21:51:14 gaz kernel: [79916.418302] php5-cgi[20089]: segfault at 1c59dc8 ip 0000000001c59dc8 sp 00007fff9b877fb8 error 15 Mar 3 03:45:01 gaz kernel: [101143.334305] munin-update[22519] general protection ip:7f516dce204c sp:7fff6049a978 error:0 in libperl.so.5.10.1[7f516dc7d000+164000] Mar 3 11:22:37 gaz kernel: [128599.570307] php5-cgi[22888]: segfault at 36485a8 ip 00000000036485a8 sp 00007fff2d56e1c8 error 15 Mar 4 08:32:17 gaz kernel: [204779.842304] php5-cgi[22090]: segfault at 18 ip 0000000000689e5e sp 00007fff677a6a48 error 6 in php5-cgi[400000+6f9000] Mar 4 10:01:02 gaz kernel: [210104.434706] rsync[22236] general protection ip:7f14a07137f9 sp:7fff88f940b8 error:0 in libc-2.11.2.so[7f14a069d000+158000] Mar 4 11:32:22 gaz kernel: [215584.262316] BUG: unable to handle kernel paging request at 00000000ffffff9c Mar 4 11:32:22 gaz kernel: [215584.262331] IP: [<00000000ffffff9c>] 0xffffff9c Mar 4 11:32:22 gaz kernel: [215584.262343] PGD 0 Mar 4 11:32:22 gaz kernel: [215584.262350] Oops: 0010 [#2] SMP Mar 4 11:32:22 gaz kernel: [215584.262359] last sysfs file: /sys/devices/pci0000:00/0000:00:12.0/host4/target4:0:0/4:0:0:0/block/sdb/stat Mar 4 11:32:22 gaz kernel: [215584.262371] CPU 1 Mar 4 11:32:22 gaz kernel: [215584.262378] Modules linked in: cpufreq_userspace cpufreq_stats cpufreq_powersave cpufreq_conservative xt_recent xt_tcpudp iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 ip6table_filter ip6_tables xt_DSCP xt_TCPMSS ipt_LOG ipt_REJECT iptable_mangle iptable_filter xt_multiport xt_state xt_limit xt_conntrack nf_conntrack_ftp nf_conntrack ip_tables x_tables loop snd_hda_codec_atihdmi snd_hda_intel snd_hda_codec snd_hwdep snd_pcm radeon snd_timer ttm snd drm_kms_helper soundcore drm snd_page_alloc i2c_algo_bit shpchp i2c_piix4 edac_core pcspkr k8temp evdev edac_mce_amd pci_hotplug i2c_core button ext3 jbd mbcache dm_mod powernow_k8 aacraid 3w_9xxx 3w_xxxx raid10 raid456 async_raid6_recov async_pq raid6_pq async_xor xor async_memcpy async_tx raid1 raid0 md_mod sata_nv sata_sil sata_via sd_mod crc_t10dif ata_generic ahci pata_atiixp ohci_hcd libata r8169 mii thermal ehci_hcd processor thermal_sys scsi_mod usbcore nls_base [last unloaded: scsi_wait_scan] Mar 4 11:32:22 gaz kernel: [215584.262552] Pid: 1960, comm: proxymap Tainted: G D 2.6.32-5-amd64 #1 MS-7368 Mar 4 11:32:22 gaz kernel: [215584.262563] RIP: 0010:[<00000000ffffff9c>] [<00000000ffffff9c>] 0xffffff9c Mar 4 11:32:22 gaz kernel: [215584.262573] RSP: 0018:ffff880209257e00 EFLAGS: 00010212 Mar 4 11:32:22 gaz kernel: [215584.262580] RAX: ffff8801514eb780 RBX: ffffffff810efb2d RCX: 0000000000000000 Mar 4 11:32:22 gaz kernel: [215584.262590] RDX: 0000000000000020 RSI: 0000000000000001 RDI: ffff8801514eb780 Mar 4 11:32:22 gaz kernel: [215584.262600] RBP: 00000000ffffffe9 R08: 0000000000000000 R09: 0000000000000000 Mar 4 11:32:22 gaz kernel: [215584.262611] R10: ffff880209257e78 R11: ffffffff81152c7c R12: 0000000000000001 Mar 4 11:32:22 gaz kernel: [215584.262622] R13: 0000000000008001 R14: 0000000000000024 R15: 00000000ffffff9c Mar 4 11:32:22 gaz kernel: [215584.262633] FS: 00007fca4de35700(0000) GS:ffff880008d00000(0000) knlGS:0000000000000000 Mar 4 11:32:22 gaz kernel: [215584.262644] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Mar 4 11:32:22 gaz kernel: [215584.262650] CR2: 00000000ffffff9c CR3: 00000001c9cbb000 CR4: 00000000000006e0 Mar 4 11:32:22 gaz kernel: [215584.262661] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Mar 4 11:32:22 gaz kernel: [215584.262671] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Mar 4 11:32:22 gaz kernel: [215584.262682] Process proxymap (pid: 1960, threadinfo ffff880209256000, task ffff88021c4b1c40) Mar 4 11:32:22 gaz kernel: [215584.262693] Stack: Mar 4 11:32:22 gaz kernel: [215584.262698] ffffffff810f8566 ffff880209257e78 ffff88021c7bf000 ffff88021c7bf0c8 Mar 4 11:32:22 gaz kernel: [215584.262709] <0> 0000800000000000 ffff88021fc0f000 ffff880209257e78 00000000fffffffe Mar 4 11:32:22 gaz kernel: [215584.262724] <0> ffffffff810e5881 ffff880209257f48 0000000000000286 ffff88021fc0f000 Mar 4 11:32:22 gaz kernel: [215584.262743] Call Trace: Mar 4 11:32:22 gaz kernel: [215584.262753] [<ffffffff810f8566>] ? do_filp_open+0xa7/0x94b Mar 4 11:32:22 gaz kernel: [215584.262763] [<ffffffff810e5881>] ? virt_to_head_page+0x9/0x2a Mar 4 11:32:22 gaz kernel: [215584.262771] [<ffffffff810f9904>] ? user_path_at+0x52/0x79 Mar 4 11:32:22 gaz kernel: [215584.262779] [<ffffffff810cfec1>] ? get_unmapped_area+0xd7/0x139 Mar 4 11:32:22 gaz kernel: [215584.262787] [<ffffffff811019d5>] ? alloc_fd+0x67/0x10c Mar 4 11:32:22 gaz kernel: [215584.262795] [<ffffffff810eceaf>] ? do_sys_open+0x55/0xfc Mar 4 11:32:22 gaz kernel: [215584.262804] [<ffffffff81010b42>] ? system_call_fastpath+0x16/0x1b Mar 4 11:32:22 gaz kernel: [215584.262811] Code: Bad RIP value. Mar 4 11:32:22 gaz kernel: [215584.262819] RIP [<00000000ffffff9c>] 0xffffff9c Mar 4 11:32:22 gaz kernel: [215584.262828] RSP <ffff880209257e00> Mar 4 11:32:22 gaz kernel: [215584.262833] CR2: 00000000ffffff9c Mar 4 11:32:22 gaz kernel: [215584.263077] ---[ end trace 1cc1473b539c7f6f ]--- As you can see there are segfaults, a general protection fault and a Kernel Oops. My first guess was that there's a Hardware problem of some sort and I asked my Hoster (it's a rented root server) to do a full hardwarecheck - they did, but couldn't find any problem. I don't know what and how they checked but their support team is usually quite good. I ran memtester and cpuburn myself and couldn't find any error either. Unfortunately I have no reliable way to reproduce these segfaults, they seem to be more or less random. On a hunch I disabled the firewall of the system and ran one of the programs that segfaulted regularily (imapsync) and it seemed to take longer to segfault than before, so the problem might be related to the network stack. Or could just be a random thing. Here are the kernel specs: # uname -a Linux gaz 2.6.32-5-amd64 #1 SMP Wed Jan 12 03:40:32 UTC 2011 x86_64 GNU/Linux # cat /etc/debian_version 6.0 # lsmod Module Size Used by cpufreq_userspace 1992 0 cpufreq_stats 2659 0 cpufreq_powersave 902 0 cpufreq_conservative 5162 0 xt_recent 5977 0 xt_tcpudp 2319 0 iptable_nat 4299 0 nf_nat 13388 1 iptable_nat nf_conntrack_ipv4 9833 3 iptable_nat,nf_nat nf_defrag_ipv4 1139 1 nf_conntrack_ipv4 ip6table_filter 2384 0 ip6_tables 15075 1 ip6table_filter xt_DSCP 1995 0 xt_TCPMSS 2919 0 ipt_LOG 4518 0 ipt_REJECT 1953 0 iptable_mangle 2817 0 iptable_filter 2258 0 xt_multiport 2267 0 xt_state 1303 0 xt_limit 1782 0 xt_conntrack 2407 0 nf_conntrack_ftp 5537 0 nf_conntrack 46535 6 iptable_nat,nf_nat,nf_conntrack_ipv4,xt_state,xt_conntrack,nf_conntrack_ftp ip_tables 13899 3 iptable_nat,iptable_mangle,iptable_filter x_tables 12845 13 xt_recent,xt_tcpudp,iptable_nat,ip6_tables,xt_DSCP,xt_TCPMSS,ipt_LOG,ipt_REJECT,xt_multiport,xt_state,xt_limit,xt_conntrack,ip_tables loop 11799 0 radeon 573996 0 ttm 39986 1 radeon drm_kms_helper 20065 1 radeon snd_hda_codec_atihdmi 2251 1 drm 142359 3 radeon,ttm,drm_kms_helper snd_hda_intel 20019 0 i2c_algo_bit 4225 1 radeon pcspkr 1699 0 i2c_piix4 8328 0 snd_hda_codec 54244 2 snd_hda_codec_atihdmi,snd_hda_intel i2c_core 15712 5 radeon,drm_kms_helper,drm,i2c_algo_bit,i2c_piix4 snd_hwdep 5380 1 snd_hda_codec snd_pcm 60503 2 snd_hda_intel,snd_hda_codec snd_timer 15582 1 snd_pcm snd 46446 5 snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_timer soundcore 4598 1 snd evdev 7352 3 snd_page_alloc 6249 2 snd_hda_intel,snd_pcm k8temp 3283 0 edac_core 29261 0 edac_mce_amd 6433 0 shpchp 26264 0 pci_hotplug 21203 1 shpchp button 4650 0 ext3 106518 2 jbd 37085 1 ext3 mbcache 5050 1 ext3 dm_mod 53754 0 powernow_k8 10978 1 aacraid 59779 0 3w_9xxx 28684 0 3w_xxxx 20569 0 raid10 17809 0 raid456 44500 0 async_raid6_recov 5170 1 raid456 async_pq 3479 2 raid456,async_raid6_recov raid6_pq 77179 2 async_raid6_recov,async_pq async_xor 2478 3 raid456,async_raid6_recov,async_pq xor 4380 1 async_xor async_memcpy 1198 2 raid456,async_raid6_recov async_tx 1734 5 raid456,async_raid6_recov,async_pq,async_xor,async_memcpy raid1 18431 3 raid0 5517 0 md_mod 73824 7 raid10,raid456,raid1,raid0 sata_nv 19166 0 sata_sil 7412 0 sata_via 7928 0 sd_mod 29889 8 crc_t10dif 1276 1 sd_mod ata_generic 3047 0 ahci 32374 6 r8169 29229 0 mii 3210 1 r8169 thermal 11674 0 pata_atiixp 3489 0 libata 133632 6 sata_nv,sata_sil,sata_via,ata_generic,ahci,pata_atiixp ohci_hcd 19212 0 ehci_hcd 31151 0 processor 29935 1 powernow_k8 thermal_sys 11942 2 thermal,processor scsi_mod 122149 5 aacraid,3w_9xxx,3w_xxxx,sd_mod,libata usbcore 122034 3 ohci_hcd,ehci_hcd nls_base 6377 1 usbcore # free total used free shared buffers cached Mem: 8166128 1228036 6938092 0 140412 782060 -/+ buffers/cache: 305564 7860564 Swap: 2102456 0 2102456 So, basically my questions are: How can I diagnose this further? Is there any data in the log above that could help me to isolate the troublemaker? Are there any known problems with the above hardware/software I overlooked when googling for it? Is there a way to prevent the kernel from autoloading modules (I probably don't need all these modules and one of them might be the culprit)

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• SQL Down Under Podcast 50 - Guest Louis Davidson now online

  - by Greg Low

  Hi Folks,I've recorded an interview today with SQL Server MVP Louis Davidson. In it, Louis discusses some of his thoughts on database design and his latest book.You'll find the podcast here: http://www.sqldownunder.com/Resources/Podcast.aspxAnd you'll find his latest book (Pro SQL Server 2012 Relational Database Design and Implementation) here: http://www.amazon.com/Server-Relational-Database-Implementation-Professional/dp/1430236957/ref=sr_1_2?ie=UTF8&qid=1344997477&sr=8-2&keywords=louis+davidsonEnjoy!

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• Control layout using graphviz twopi

  - by vy32

  I am trying to draw a graph showing search prefixes using twopi. I have a simple input file and am getting this output: (full image) Here is the input file: digraph search { // ordering=out; // color=blue; // rank=same; // overlap=scale; rankdir=LR; root=root; ranksep=1.25; overlap=true; "root"; a [color=none,fontsize=12]; b [color=none,fontsize=12]; c [color=none,fontsize=12]; d [color=none,fontsize=12]; e [color=none,fontsize=12]; f [color=none,fontsize=12]; #g [color=none,fontsize=12]; h [color=none,fontsize=12]; i [color=none,fontsize=12]; j [color=none,fontsize=12]; k [color=none,fontsize=12]; l [color=none,fontsize=12]; m [color=none,fontsize=12]; n [color=none,fontsize=12]; o [color=none,fontsize=12]; p [color=none,fontsize=12]; q [color=none,fontsize=12]; r [color=none,fontsize=12]; s [color=none,fontsize=12]; t [color=none,fontsize=12]; u [color=none,fontsize=12]; v [color=none,fontsize=12]; w [color=none,fontsize=12]; x [color=none,fontsize=12]; y [color=none,fontsize=12]; #ga [color=none,fontsize=12]; gb [color=none,fontsize=12]; gc [color=none,fontsize=12]; gd [color=none,fontsize=12]; ge [color=none,fontsize=12]; gf [color=none,fontsize=12]; gg [color=none,fontsize=12]; gh [color=none,fontsize=12]; gi [color=none,fontsize=12]; gj [color=none,fontsize=12]; gk [color=none,fontsize=12]; gl [color=none,fontsize=12]; gm [color=none,fontsize=12]; gn [color=none,fontsize=12]; go [color=none,fontsize=12]; gp [color=none,fontsize=12]; gq [color=none,fontsize=12]; gr [color=none,fontsize=12]; gs [color=none,fontsize=12]; gt [color=none,fontsize=12]; gu [color=none,fontsize=12]; gv [color=none,fontsize=12]; gw [color=none,fontsize=12]; gx [color=none,fontsize=12]; gy [color=none,fontsize=12]; gaa [color=none,fontsize=12]; gab [color=none,fontsize=12]; gac [color=none,fontsize=12]; gad [color=none,fontsize=12]; gae [color=none,fontsize=12]; gaf [color=none,fontsize=12]; gag [color=none,fontsize=12]; gah [color=none,fontsize=12]; gai [color=none,fontsize=12]; gaj [color=none,fontsize=12]; gak [color=none,fontsize=12]; gal [color=none,fontsize=12]; gam [color=none,fontsize=12]; gan [color=none,fontsize=12]; gao [color=none,fontsize=12]; gap [color=none,fontsize=12]; gaq [color=none,fontsize=12]; #gaz [color=none,fontsize=12]; gas [color=none,fontsize=12]; gat [color=none,fontsize=12]; gau [color=none,fontsize=12]; gav [color=none,fontsize=12]; gaw [color=none,fontsize=12]; gax [color=none,fontsize=12]; gay [color=none,fontsize=12]; gaza [color=none,fontsize=12]; gazb [color=none,fontsize=12]; gazc [color=none,fontsize=12]; gazd [color=none,fontsize=12]; gaze [color=none,fontsize=12]; #gazf [color=none,fontsize=12]; gazg [color=none,fontsize=12]; gazh [color=none,fontsize=12]; gazi [color=none,fontsize=12]; gazj [color=none,fontsize=12]; gazk [color=none,fontsize=12]; gazl [color=none,fontsize=12]; gazm [color=none,fontsize=12]; gazn [color=none,fontsize=12]; gazo [color=none,fontsize=12]; gazp [color=none,fontsize=12]; gazq [color=none,fontsize=12]; gazr [color=none,fontsize=12]; gazs [color=none,fontsize=12]; gazt [color=none,fontsize=12]; gazu [color=none,fontsize=12]; gazv [color=none,fontsize=12]; gazw [color=none,fontsize=12]; gazx [color=none,fontsize=12]; gazy [color=none,fontsize=12]; root -> a [minlen=2]; root -> b [minlen=2]; root -> c [minlen=2]; root -> d [minlen=2]; root -> e [minlen=2]; root -> f [minlen=2]; root -> g [minlen=2]; root -> h [minlen=2]; root -> i [minlen=2]; root -> j [minlen=2]; root -> k [minlen=2]; root -> l [minlen=2]; root -> m [minlen=2]; root -> n [minlen=2]; root -> o [minlen=2]; root -> p [minlen=2]; root -> q [minlen=2]; root -> r [minlen=2]; root -> s [minlen=20]; root -> t [minlen=2]; root -> u [minlen=2]; root -> v [minlen=2]; root -> w [minlen=2]; root -> x [minlen=2]; root -> y [minlen=2]; root -> 0 [minlen=2]; root -> 1 [minlen=2]; root -> 2 [minlen=2]; root -> 3 [minlen=2]; root -> 4 [minlen=2]; root -> 5 [minlen=2]; root -> 6 [minlen=2]; root -> 7 [minlen=2]; root -> 8 [minlen=2]; root -> 9 [minlen=2]; root -> "." [minlen=2]; g -> ga ; g -> gb ; g -> gc ; g -> gd ; g -> ge ; g -> gf ; g -> gg ; g -> gh ; g -> gi ; g -> gj ; g -> gk ; g -> gl ; g -> gm ; g -> gn ; g -> go ; g -> gp ; g -> gq ; g -> gr ; g -> gs ; g -> gt ; g -> gu ; g -> gv ; g -> gw ; g -> gx ; g -> gy ; ga -> gaa ; ga -> gab ; ga -> gac ; ga -> gad ; ga -> gae ; ga -> gaf ; ga -> gag ; ga -> gah ; ga -> gai ; ga -> gaj ; ga -> gak ; ga -> gal ; ga -> gam ; ga -> gan ; ga -> gao ; ga -> gap ; ga -> gaq ; ga -> gaz ; ga -> gas ; ga -> gat ; ga -> gau ; ga -> gav ; ga -> gaw ; ga -> gax ; ga -> gay ; gaz -> gaza ; gaz -> gazb ; gaz -> gazc ; gaz -> gazd ; gaz -> gaze ; gaz -> gazf ; gaz -> gazg ; gaz -> gazh ; gaz -> gazi ; gaz -> gazj ; gaz -> gazk ; gaz -> gazl ; gaz -> gazm ; gaz -> gazn ; gaz -> gazo ; gaz -> gazp ; gaz -> gazq ; gaz -> gazr ; gaz -> gazs ; gaz -> gazt ; gaz -> gazu ; gaz -> gazv ; gaz -> gazw ; gaz -> gazx ; gaz -> gazy ; gazo -> "Blue Tuesday" ; "Blue Tuesday" [ fontsize=10]; // Layout engines: circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi } This output is generated with: twopi -os1.png -Tpng s1.dot I'm posting here because the printout is pretty dreadful. All of the nodes hung of "gaz" are overlapping; I've tried specifying nodesep and it is simply ignored. I would like to see the lines from root to the single letters further apart, but again, I can't control that. This seems to be a bug in twopi. The documentation says it should clearly follow these directives, but it doesn't seem to. My questions: Is there any way to make twopi behave? Failing that, is there a better layout engine to use? Thanks.

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• Ruby File IO question; Maintain file read position between script executions

  - by macek

  I have two files a.txt and b.txt (henceforth a and b). My script iterates through a, does some operation, and potentially inserts a line to b. In the event the script stops, I need it to pick up where it left off. In the example below: foo was copied to b bar was copied to b zim was not copied to b (did not pass some criteria) gaz was copied to b Script stops (for whatever reason) When script starts again, how to open a and start on line "dib"? a.txt foo bar zim gaz // <= last successful copy dib // <= I want to start here on next script execution gir b.txt foo bar gaz // <= note omission of "zim" above gaz

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• Introducing Glimpse – Firebug for your server

  - by Neil Davidson

  Here at Red Gate, we spend every waking hour trying to wow .NET and SQL developers with great products.  Every so often, though, we find something out in the wild which knocks our socks off by taking “ingeniously simple” to a whole new level.  That’s what a little community led by developers Nik Molnar and Anthony van der Hoorn has done with the open source tool Glimpse. Glimpse describes itself as ‘Firebug for the server.’  You drop the NuGet package into your ASP.NET project, and then — like magic* — your web pages will bare every detail of their execution.  Even by our high standards, it was trivial to get running: if you can use NuGet, you’re already there. You get all that lovely detail without changing any code. Our feelings go beyond respect for the developers who designed and wrote Glimpse; we’re thrilled that Nik and Anthony have come to work for Red Gate full-time. They’re going to stay in control of the project and keep doing open source development work on Glimpse.  In the medium term, we’re hoping to make paid-for products which plug into the free open source framework, especially in areas like performance profiling where we already have some deep technology.  First, though, Glimpse needs to get from beta to a v1. Given the breakneck pace of new development, this should only be a month or so away. Supporting an open source project is a first for Red Gate, so we’re going to be working with Nik and Anthony, with the Glimpse community and even with other vendors to figure out what ‘great’ looks like from the a user perspective.  Only one thing is certain: this technology deserves a wider audience than the 40,000 people who have already downloaded it, so please have a look and tell us what you think. You can hear more about what the Glimpse developers think on the Glimpse blog, and there are plenty more technical facts over at our product manager’s blog. If you have any questions or queries, please tweet with the #glimpse hashtag or contact the Glimpse team directly on [email protected]. [*That’s ”magic” in the Arthur C. Clarke “sufficiently advanced technology” sense, of course] Neil Davidson co-founder and Joint CEO Red Gate Software http://twitter.com/neildavidson    

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• Android: Cannot cast from View to MapView

  - by Gaz

  I'm trying to run the Android MapView example, and am getting a 'Cannot cast from View to MapView' error in Eclipse. My layout is as follows <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainlayout" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <com.google.android.maps.MapView android:id="@+id/mapview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:clickable="true" android:apiKey="0jwi0saLYCPGfO-t7glg5bQoBz7jVKWCcgyQWQA" /> <LinearLayout android:id="@+id/zoomview" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBottom="@id/mapview" android:layout_centerHorizontal="true" /> </RelativeLayout> and the Activity code is package org.gaz.mapapp; import android.os.Bundle; import android.view.View; import android.widget.LinearLayout; import android.widget.ZoomControls; import com.google.android.maps.*; public class MapView extends MapActivity { LinearLayout linearLayout; MapView mapView; ZoomControls mZoom; public void onCreate(Bundle savedInstance) { linearLayout = (LinearLayout) findViewById(R.id.mainlayout); mapView = (MapView) findViewById(R.id.mapview); mZoom = (ZoomControls) mapView.getZoomControls(); } @Override protected boolean isRouteDisplayed() { // TODO Auto-generated method stub return false; } } The error is caused by the line mapView = (MapView) findViewById(R.id.mapview); Can anybody offer an suggestions as to a fix? Cheers, Gaz.

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• Android Xperia X10 SoundPool

  - by Gaz

  Hi All, I have had some reports from users of my android app that there is no sound being played on the X10. I'm a bit confused as it works on all other phones that I have tried, Neus One, Hero, Droid. I'm using the SoundPool class to play sounds, has anybody else had similar issues with the X10? Thanks, Gaz

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• jCarouselLite not setting width and left values on div

  - by Gaz

  Hi, jCarouselLite not setting width and left values on div. Also, in firebug the div and ul and greyed out although the div has: visibility: visible; Incidently, the width and height attributes on the ul and subsequent li's are set to 0, shouldn't jCarouselLite be setting those? Images are being loaded in the DOM - but not displaying. Thanks, Gaz

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• Validating form dropdown in CodeIgniter

  - by Gaz

  Hi, I am using CodeIgniter's form helper and form validation library to build my forms. I'm having trouble making the dropdown 'sticky' and also finding appropriate validation rules. This is how I'm populating the drodown: foreach($events as $event){ $options[$event->event_title] = $event->event_title; } $firstItem = '<option>Please select one...</option>'; echo form_dropdown('events', $options, '', $firstItem); This is building the options from events stored in the database. The form looks fine and is populating tall the fields correctly. Hwoever, when I come to submit the form, the dropdown isn't holding onto the value selected? Also, how should I validate it, I want to make it required but I also want to make sure that I dont except the first option in the dropdown 'Please select one...' Thanks in advance. Cheers, Gaz

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• Mouse not working after upgrade

  - by Gaz

  After upgrade from 12.4 to 13.4 my usb mouse does not respond. Unlike similar posts my keyboard works (Alt + Tab, num loc etc) which means I can enter password and still log into desktop but still with no mouse support. I have tried other usb and PS2 mice (Logitech and Microsoft mouse) that are working on other Systems with no success. When running "xsetpointer -1 | grep Pointer" in terminal window as per post USB Mouse not recognized it shows no mouse installed. When the mouse is plugged in the light under mouse illuminates so their is power to mouse. In KDE by using the keyboard I was able to turn on "Move pointer with keyboard (using num pad)" from the "Mouse - KDE Control Module" which allowed me to move the mouse pointer using the keyboard. Without complete reinstall how do I get mouse working again?

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• What Counts For a DBA: Simplicity

  - by Louis Davidson

  Too many computer processes do an apparently simple task in a bizarrely complex way. They remind me of this strip by one of my favorite artists: Rube Goldberg. In order to keep the boss from knowing one was late, a process is devised whereby the cuckoo clock kisses a live cuckoo bird, who then pulls a string, which triggers a hat flinging, which in turn lands on a rod that removes a typewriter cover…and so on. We rely on creating automated processes to keep on top of tasks. DBAs have a lot of tasks to perform: backups, performance tuning, data movement, system monitoring, and of course, avoiding being noticed.  Every day, there are many steps to perform to maintain the database infrastructure, including: checking physical structures, re-indexing tables where needed, backing up the databases, checking those backups, running the ETL, and preparing the daily reports and yes, all of these processes have to complete before you can call it a day, and probably before many others have started that same day. Some of these tasks are just naturally complicated on their own. Other tasks become complicated because the database architecture is excessively rigid, and we often discover during “production testing” that certain processes need to be changed because the written requirements barely resembled the actual customer requirements.   Then, with no time to change that rigid structure, we are forced to heap layer upon layer of code onto the problematic processes. Instead of a slight table change and a new index, we end up with 4 new ETL processes, 20 temp tables, 30 extra queries, and 1000 lines of SQL code.  Report writers then need to build reports and make magical numbers appear from those toxic data structures that are overly complex and probably filled with inconsistent data. What starts out as a collection of fairly simple tasks turns into a Goldbergian nightmare of daily processes that are likely to cause your dinner to be interrupted by the smartphone doing the vibration dance that signifies trouble at the mill. So what to do? Well, if it is at all possible, simplify the problem by either going into the code and refactoring the complex code to simple, or taking all of the processes and simplifying them into small, independent, easily-tested steps.  The former approach usually requires an agreement on changing underlying structures that requires countless mind-numbing meetings; while the latter can generally be done to any complex process without the same frustration or anger, though it will still leave you with lots of steps to complete, the ability to test each step independently will definitely increase the quality of the overall process (and with each step reporting status back, finding an actual problem within the process will be definitely less unpleasant.) We all know the principle behind simplifying a sequence of processes because we learned it in math classes in our early years of attending school, starting with elementary school. In my 4 years (ok, 9 years) of undergraduate work, I remember pretty much one thing from my many math classes that I apply daily to my career as a data architect, data programmer, and as an occasional indentured DBA: “show your work”. This process of showing your work was my first lesson in simplification. Each step in the process was in fact, far simpler than the entire process.  When you were working an equation that took both sides of 4 sheets of paper, showing your work was important because the teacher could see every step, judge it, and mark it accordingly.  So often I would make an error in the first few lines of a problem which meant that the rest of the work was actually moving me closer to a very wrong answer, no matter how correct the math was in the subsequent steps. Yet, when I got my grade back, I would sometimes be pleasantly surprised. I passed, yet missed every problem on the test. But why? While I got the fact that 1+1=2 wrong in every problem, the teacher could see that I was using the right process. In a computer process, the process is very similar. We take complex processes, show our work by storing intermediate values, and test each step independently. When a process has 100 steps, each step becomes a simple step that is tested and verified, such that there will be 100 places where data is stored, validated, and can be checked off as complete. If you get step 1 of 100 wrong, you can fix it and be confident (that if you did your job of testing the other steps better than the one you had to repair,) that the rest of the process works. If you have 100 steps, and store the state of the process exactly once, the resulting testable chunk of code will be far more complex and finding the error will require checking all 100 steps as one, and usually it would be easier to find a specific needle in a stack of similarly shaped needles.  The goal is to strive for simplicity either in the solution, or at least by simplifying every process down to as many, independent, testable, simple tasks as possible.  For the tasks that really can’t be done completely independently, minimally take those tasks and break them down into simpler steps that can be tested independently.  Like working out division problems longhand, have each step of the larger problem verified and tested.

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• What Counts For a DBA: Ego

  - by Louis Davidson

  Leaving aside, for a second, Freud’s psychoanalytical definitions, the term “ego” generally refers to a person’s sense of self, and their self-esteem. In casual usage, however, it usually appears in the adjectival form, “egotistical” (most often followed by “jerk”). You don’t need to be a jerk to be a DBA; humility is important. However, ego is important too. A good DBA needs a certain degree of self-esteem…a belief and pride in what he or she can do better than anyone else can. The ideal DBA needs to be humble enough to admit when they are wrong but egotistical enough to know when they are right, and to stand up for that knowledge and make their voice heard. In most organizations, the DBA team is seriously outnumbered by headstrong developers and clock driven managers, and “great” DBAs will often be outnumbered by…well…the not so great. In order to be heard in this environment, a DBA will not only need to be very skilled, but will also need a healthy dose of ego. As Freud might have put it, the unconscious desire of the DBA (the id) is for iron-fist control over their databases, and code that runs in them. However, the ego moderates this desire, seeking to “satisfy the id in realistic ways that, in the long term, bring benefit rather than grief“. In other words, the ego understands the need to exert a measure of control and self-belief, but also to tolerate and play nicely with developers and other DBAs. The trick, naturally, is learning how to be heard when it is important, but also to make everyone around you welcome that input, even when you have to be bold to make the “I know what I am talking about, and you…well…not so much” decisions. Consider a baseball team, bottom of the ninth inning of the championship game, man on first and down one run. Almost anyone on that team will have the ability to hit a home run, but only one or two will have the iron belief that they can pull it off in this critical, end-game situation. The player you need in this situation is the one who has passionately gone the extra mile preparing for just this moment, is bursting at the seams with self-confidence, and can look the coach in the eye and state, boldly, “Put me in, I am your best bet“. Likewise, on those occasions when high customer demand coincides with copious system errors, and panic is bubbling just beneath the surface, you don’t need the minimally qualified support person, armed with the “reboot and hope” technique (though that sometimes works!). You need the DBA who steps up and says, “Put me in” and has the skill and tenacity to back up those words and to fix the pinpoint and fix the problem, whatever it takes, while keeping customers and managers happy. Of course, the egotistical DBA will happily spend hours telling you how great they are at their job, and how brilliantly they put out a previous fire, and this is no guarantee that they can deliver. However, if an otherwise-humble DBA looks you in the eye and says, “I can do it”, then hear them out. Sometimes, this burst of ego will be exactly what’s required.

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• What Counts For a DBA – Decisions

  - by Louis Davidson

  It’s Friday afternoon, and the lead DBA, a very talented guy, is getting ready to head out for two well-earned weeks of vacation, with his family, when this error message pops up in his inbox: Msg 211, Level 23, State 51, Line 1. Possible schema corruption. Run DBCC CHECKCATALOG. His heart sinks. It’s ten…no eight…minutes till it’s time to walk out the door. He glances around at his coworkers, competent to handle many problems, but probably not up to the challenge of fixing possible database corruption. What does he do? After a few agonizing moments of indecision, he clicks shut his laptop. He’ll just wait and see. It was unlikely to come to anything; after all, it did say “possible” schema corruption, not definite. In that moment, his fate was sealed. The start of the solution to the problem (run DBCC CHECKCATALOG) had been right there in the error message. Had he done this, or at least took two of those eight minutes to delegate the task to a coworker, then he wouldn’t have ended up spending two-thirds of an idyllic vacation (for the rest of the family, at least) dealing with a problem that got consistently worse as the weekend progressed until the entire system was down. When I told this story to a friend of mine, an opera fan, he smiled and said it described the basic plotline of almost every opera or ‘Greek Tragedy’ ever written. The particular joy in opera, he told me, isn’t the warbly voiced leading ladies, or the plump middle-aged romantic leads, or even the music. No, what packs the opera houses in Italy is the drama of characters who, by the very nature of their life-experiences and emotional baggage, make all sorts of bad choices when faced with ordinary decisions, and so move inexorably to their fate. The audience is gripped by the spectacle of exotic characters doomed by their inability to see the obvious. I confess, my personal experience with opera is limited to Bugs Bunny in “What’s Opera, Doc?” (Elmer Fudd is a great example of a bad decision maker, if ever one existed), but I was struck by my friend’s analogy. If all the DBA cubicles were a stage, I think we would hear many similarly tragic tales, played out to music: “Error handling? We write our code to never experience errors, so nah…“ “Backups failed today, but it’s okay, we’ll back up tomorrow (we’ll back up tomorrow)“ And similarly, they would leave their audience gasping, not necessarily at the beauty of the music, or poetry of the lyrics, but at the inevitable, grisly fate of the protagonists. If you choose not to use proper error handling, or if you choose to skip a backup because, hey, you haven’t had a server crash in 10 years, then inevitably, in that moment you expected to be enjoying a vacation, or a football game, with your family and friends, you will instead be sitting in front of a computer screen, paying for your poor choices. Tragedies are very much part of IT. Most of a DBA’s day to day work has limited potential to wreak havoc; paperwork, timesheets, random anonymous threats to developers, routine maintenance and whatnot. However, just occasionally, you, as a DBA, will face one of those decisions that really matter, and which has the possibility to greatly affect your future and the future of your user’s data. Make those decisions count, and you’ll avoid the tragic fate of many an operatic hero or villain.

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• Latest Edition of Security Inside Out Newsletter Now Available

  - by Troy Kitch

  The latest edition of Security Inside Out newsletter is now available. If you don't get this bi-monthly security newsletter in your inbox, then subscribe to get the latest database security news. This bi-monthly edition includes: Q&A: Oracle CSO Mary Ann Davidson on Meeting Tomorrow's Security Threats Oracle Chief Security Officer Mary Ann Davidson shares her thoughts on next-generation security threats.  Read More New Study: Increased Security Spending Still Not Protecting Right Assets Despite widespread belief that database breaches represent the greatest security risk to their business, organizations continue to devote a far greater share of their security resources to network assets rather than database assets, according to a new report issued by CSO and sponsored by Oracle. Read More

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• What Counts For A DBA: ESP

  - by Louis Davidson

  Now I don’t want to get religious here, and I’m not going to, but what I’m going to describe in this ‘What Counts for a DBA’ installment sometimes feels like magic. Often  I will spend hours thinking about the solution to a design issue or coding problem, working diligently to try to come up with a solution and then finally just give up with the feeling that I’m not even qualified to be a data entry clerk, much less a data architect.  At this point I often take a walk (or sometimes a nap), and then it hits me. I realize that I have the answer just sitting in my brain, ready to implement.  This phenomenon is not limited to walks either; it can happen almost any time after I stop my obsession about a problem. I call this phenomena ESP (or Extra-Sensory Programming.)  Another term for this could be ‘sleeping on it’, and while the idiom tends to mean to let time pass to actively think about a problem, sleeping on a problem also lets you relax and let your brain do the work. I first noticed this back in my college days when I would play video games for hours on end. We would get stuck deep in some dungeon unable to find a way out, playing for days on end until we were beaten down tired. Once we gave up and walked away, the solution would usually be there waiting for one of us before we came back to play the next day.  Sometimes it would be in the form of a dream, and sometimes it would just be that the problem was now easy to solve when we started to play again.  While it worked great for video games, it never occurred when I studied English Literature for hours on end, or even when I worked for the same sort of frustrating hours attempting to solve a homework problem in Calculus.  I believe that the difference was that I was passionate about the video game, and certainly far less so about homework where people used the word “thou” instead of “you” or x to represent a number. This phenomenon occurs somewhat more often in my current work as a professional data programmer, because I am very passionate about SQL and love those aspects of my career choice.  Every day that I get to draw a new data model to solve a customer issue, or write a complex SELECT statement to ferret out the answer to a complex data question, is a great day. I hope it is the same for any reader of this blog.  But, unfortunately, while the day on a whole is great, a heck of a lot of noise is generated in work life. There are the typical project deadlines, along with the requisite project manager sitting on your shoulders shouting slogans to try to make you to go faster: Add in office politics, and the occasional family issues that permeate the mind, and you lose the ability to think deeply about any problem, not to mention occasionally forgetting your own name.  These office realities coupled with a difficult SQL problem staring at you from your widescreen monitor will slowly suck the life force out of your body, making it seem impossible to solve the problem This is when the walk starts; or a nap. Maybe you hide from the madness under your desk like George Costanza hides from Steinbrenner on Seinfeld.  Forget about the problem. Free your mind from the insanity of the problem and your surroundings. Then let your training and education deep in your brain take over and see if it will passively do the rest for you. If you don’t end up with a solution, the worst case scenario is that you have a bit of exercise or rest, and you won’t have heard the phrase “better is the enemy of good enough” even once…which certainly will do your brain some good. Once you stop expecting whipping your brain for information, inspiration may just strike and instead of a humdrum solution you find a solution you hadn’t even considered, almost magically. So, my beloved manager, next time you have an urgent deadline and you come across me taking a nap, creep away quietly because I’m working, doing some extra-sensory programming.

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• What Counts For a DBA: Replaceable

  - by Louis Davidson

  Replaceable is what every employee in every company instinctively strives not to be. Yet, if you’re an irreplaceable DBA, meaning that the company couldn’t find someone else who could do what you do, then you’re not doing a great job. A good DBA is replaceable. I imagine some of you are already reaching for the lighter fluid, about to set the comments section ablaze, but before you destroy a perfectly good Commodore 64, read on… Everyone is replaceable, ultimately. Anyone, anywhere, in any job, could be sitting at their desk reading this, blissfully unaware that this is to be their last day at work. Morbidly, you could be about to take your terminal breath. Ideally, it will be because another company suddenly offered you a truck full of money to take a new job, forcing you to bid a regretful farewell to your current employer (with barely a “so long suckers!” left wafting in the air as you zip out of the office like the Wile E Coyote wearing two pairs of rocket skates). I’ve often wondered what it would be like to be present at the meeting where your former work colleagues discuss your potential replacement. It is perhaps only at this point, as they struggle with the question “What kind of person do we need to replace old Wile?” that you would know your true worth in their eyes. Of course, this presupposes you need replacing. I’ve known one or two people whose absence we adequately compensated with a small rock, to keep their old chair from rolling down a slight incline in the floor. On another occasion, we bought a noise-making machine that frequently attracted attention its way, with unpleasant sounds, but never contributed anything worthwhile. These things never actually happened, of course, but you take my point: don’t confuse replaceable with expendable. Likewise, if the term “trained seal” comes up, someone they can teach to follow basic instructions and push buttons in the right order, then the replacement discussion is going to be over quickly. What, however, if your colleagues decide they’ll need a super-specialist to replace you. That’s a good thing, right? Well, usually, in my experience, no it is not. It often indicates that no one really knows what you do, or how. A typical example is the “senior” DBA who built a system just before 16-bit computing became all the rage and then settled into a long career managing it. Such systems are often central to the company’s operations and the DBA very skilled at what they do, but almost impossible to replace, because the system hasn’t evolved, and runs on processes and routines that others no longer understand or recognize. The only thing you really want to hear, at your replacement discussion, is that they need someone skilled at the fundamentals and adaptable. This means that the person they need understands that their goal is to be an excellent DBA, not a specialist in whatever the-heck the company does. Someone who understands the new versions of SQL Server and can adapt the company’s systems to the way things work today, who uses industry standard methods that any other qualified DBA/programmer can understand. More importantly, this person rarely wants to get “pigeon-holed” and so documents and shares the specialized knowledge and responsibilities with their teammates. Being replaceable doesn’t mean being “dime a dozen”. The company might need four people to take your place due to the depth of your skills, but still, they could find those replacements and those replacements could step right in using techniques that any decent DBA should know. It is a tough question to contemplate, but take some time to think about the sort of person that your colleagues would seek to replace you. If you think they would go looking for a “super-specialist” then consider urgently how you can diversify and share your knowledge, and start documenting all the processes you know as if today were your last day, because who knows, it just might be.

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• Looking for a short book on C# 2010 for experienced programmers

  - by Gaz Davidson

  Hi I'm an experienced programmer (C++, Java, Python, C, Objective-C, and others) and need to take a crash course in C# for my current job. I've never done any C# programming before though have read a bit about the syntax etc, I'm looking for a guide that quickly introduces advanced topics so I can get a handle on the language and begin hacking ASAP. Does anyone know of such a book? Amazon and Google are drawing a blank. Thanks in advance!

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• DBA in Space

  - by Neil Davidson

  Every now and then, you come across an idea that makes your heart jump and your skin tingle. That happened to me a few months ago, when Richard and Anthony pitched a small group of us an idea. "It's called DBA in Space", Richard said. I don't remember the rest of the pitch. "DBA in Space" is one of those phrases that's so simple, remarkable and clear that it sticks and it sticks hard. Sure, lots of people have done much hard, gritty work over the past few months to make it happen. Sure, there's...(read more)

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• Good DBAs Do Baselines

  - by Louis Davidson

  One morning, you wake up and feel funny. You can’t quite put your finger on it, but something isn’t quite right. What now? Unless you happen to be a hypochondriac, you likely drag yourself out of bed, get on with the day and gather more “evidence”. You check your symptoms over the next few days; do you feel the same, better, worse? If better, then great, it was some temporal issue, perhaps caused by an allergic reaction to some suspiciously spicy chicken. If the same or worse then you go to the doctor for some health advice, but armed with some data to share, and having ruled out certain possible causes that are fixed with a bit of rest and perhaps an antacid. Whether you realize it or not, in comparing how you feel one day to the next, you have taken baseline measurements. In much the same way, a DBA uses baselines to gauge the gauge health of their database servers. Of course, while SQL Server is very willing to share data regarding its health and activities, it has almost no idea of the difference between good and bad. Over time, experienced DBAs develop “mental” baselines with which they can gauge the health of their servers almost as easily as their own body. They accumulate knowledge of the daily, natural state of each part of their database system, and so know instinctively when one of their databases “feels funny”. Equally, they know when an “issue” is just a passing tremor. They see their SQL Server with all of its four CPU cores running close 100% and don’t panic anymore. Why? It’s 5PM and every day the same thing occurs when the end-of-day reports, which are very CPU intensive, are running. Equally, they know when they need to respond in earnest when it is the first time they have heard about an issue, even if it has been happening every day. Nevertheless, no DBA can retain mental baselines for every characteristic of their systems, so we need to collect physical baselines too. In my experience, surprisingly few DBAs do this very well. Part of the problem is that SQL Server provides a lot of instrumentation. If you look, you will find an almost overwhelming amount of data regarding user activity on your SQL Server instances, and use and abuse of the available CPU, I/O and memory. It seems like a huge task even to work out which data you need to collect, let alone start collecting it on a regular basis, managing its storage over time, and performing detailed comparative analysis. However, without baselines, though, it is very difficult to pinpoint what ails a server, just by looking at a single snapshot of the data, or to spot retrospectively what caused the problem by examining aggregated data for the server, collected over many months. It isn’t as hard as you think to get started. You’ve probably already established some troubleshooting queries of the type SELECT Value FROM SomeSystemTableOrView. Capturing a set of baseline values for such a query can be as easy as changing it as follows: INSERT into BaseLine.SomeSystemTable (value, captureTime) SELECT Value, SYSDATETIME() FROM SomeSystemTableOrView; Of course, there are monitoring tools that will collect and manage this baseline data for you, automatically, and allow you to perform comparison of metrics over different periods. However, to get yourself started and to prove to yourself (or perhaps the person who writes the checks for tools) the value of baselines, stick something similar to the above query into an agent job, running every hour or so, and you are on your way with no excuses! Then, the next time you investigate a slow server, and see x open transactions, y users logged in, and z rows added per hour in the Orders table, compare to your baselines and see immediately what, if anything, has changed!

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• What Counts For a DBA: Fitness

  - by Louis Davidson

  If you know me, you can probably guess that physical exercise is not really my thing. There was a time in my past when it a larger part of my life, but even then never in the same sort of passionate way as a number of our SQL friends.  For me, I find that mental exercise satisfies what I believe to be the same inner need that drives people to run farther than I like to drive on most Saturday mornings, and it is certainly just as addictive. Mental fitness shares many common traits with physical fitness, especially the need to attain it through repetitive training. I only wish that mental training burned off a bacon cheeseburger in the same manner as does jogging around a dewy park on Saturday morning. In physical training, there are at least two goals, the first of which is to be physically able to do a task. The second is to train the brain to perform the task without thinking too hard about it. No matter how long it has been since you last rode a bike, you will be almost certainly be able to hop on and start riding without thinking about the process of pedaling or balancing. If you’ve never ridden a bike, you could be a physics professor /Olympic athlete and still crash the first few times you try, even though you are as strong as an ox and your knowledge of the physics of bicycle riding makes the concept child’s play. For programming tasks, the process is very similar. As a DBA, you will come to know intuitively how to backup, optimize, and secure database systems. As a data programmer, you will work to instinctively use the clauses of Transact-SQL DML so that, when you need to group data three ways (and not four), you will know to use the GROUP BY clause with GROUPING SETS without resorting to a search engine.  You have the skill. Making it naturally then requires repetition and experience is the primary requirement, not just simply learning about a topic. The hardest part of being really good at something is this difference between knowledge and skill. I have recently taken several informative training classes with Kimball University on data warehousing and ETL. Now I have a lot more knowledge about designing data warehouses than before. I have also done a good bit of data warehouse designing of late and have started to improve to some level of proficiency with the theory. Yet, for all of this head knowledge, it is still a struggle to take what I have learned and apply it to the designs I am working on.  Data warehousing is still a task that is not yet deeply ingrained in my brain muscle memory. On the other hand, relational database design is something that no matter how much or how little I may get to do it, I am comfortable doing it. I have done it as a profession now for well over a decade, I teach classes on it, and I also have done (and continue to do) a lot of mental training beyond the work day. Sometimes the training is just basic education, some reading blogs and attending sessions at PASS events.  My best training comes from spending time working on other people’s design issues in forums (though not nearly as much as I would like to lately). Working through other people’s problems is a great way to exercise your brain on problems with which you’re not immediately familiar. The final bit of exercise I find useful for cultivating mental fitness for a data professional is also probably the nerdiest thing that I will ever suggest you do.  Akin to running in place, the idea is to work through designs in your head. I have designed more than one database system that would revolutionize grocery store operations, sales at my local Target store, the ordering process at Amazon, and ways to improve Disney World operations to get me through a line faster (some of which they are starting to implement without any of my help.) Never are the designs truly fleshed out, but enough to work through structures and processes.  On “paper”, I have designed database systems to catalog things as trivial as my Lego creations, rental car companies and my audio and video collections. Once I get the database designed mentally, sometimes I will create the database, add some data (often using Red-Gate’s Data Generator), and write a few queries to see if a concept was realistic, but I will rarely fully flesh out the database since I have no desire to do any user interface programming anymore.  The mental training allows me to keep in practice for when the time comes to do the work I love the most for real…even if I have been spending most of my work time lately building data warehouses.  If you are really strong of mind and body, perhaps you can mix a mental run with a physical run; though don’t run off of a cliff while contemplating how you might design a database to catalog the trees on a mountain…that would be contradictory to the purpose of both types of exercise.

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• What languages are the kids of today actually programming in? Does anyone have real data?

  - by Gaz Davidson

  Back in the 80s colleges were teaching Pascal because it is easy to learn, while myself and many others like me were learning BASIC because it was not only easy to learn but accessible and also fashionable (for an extremely liberal definition of fashion) It has just occurred to me that empirical data on the actual programming languages kids are choosing to use should be a good indicator of which language would be the ideal first choice for educators. Please note that this question is not "what do you think is a good programming language for kids?"

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• What Counts For a DBA – Depth

  - by Louis Davidson

  SQL Server offers very simple interfaces to many of its features. Most people could open up SSMS, connect to a server, write a simple query and see the results. Even several of the core DBA tasks are deceptively straightforward. It doesn’t take a rocket scientist to perform a basic database backup or run a trace (even using the newfangled Extended Events!). However, appearances can be deceptive, and often times it is really important that a DBA understands not just the basics of how to perform a task, but why we do a task, and how that task works. As an analogy, consider a child walking into a darkened room. Most would know that they need to turn on the light, and how to do it, so they flick the switch. But what happens if light fails to shine forth. Most would immediately tell you that you need to consider changing the light bulb. So you hop in the car and take them to the local home store and instruct them to buy a replacement. Confronted with a 40 foot display of light bulbs, how will they decide which of the hundreds of types of bulbs, of different types, fittings, shapes, colors, power and efficiency ratings, is the right choice? Obviously the main lesson the child is going to learn this day is how to use their cell phone as a flashlight so they don’t have to ask for help the next time. Likewise, when the metaphorical toddlers who use your database server have issues, they will instinctively know something is wrong, and may even have some idea what caused it, but will have no depth of knowledge to figure out the right solution. That is where the DBA comes in and attempts to save the day. However, when one looks beneath the shiny UI, SQL Server has its own “40 foot display of light bulbs”, in the form of the tremendous number of tools and the often-bewildering amount of information they can present to the DBA, to help us find issues. Unfortunately, resorting to guesswork, to trying different “bulbs” over and over, hoping to stumble on the answer. This is where the right depth of knowledge goes a long way. If we need to write a SELECT statement, then knowing the syntax and where to find the data is not enough. Knowledge of indexes and query plans is essential. Without it, we might hit on a query that “works”, but we are basically still a user, not a programmer, because we have no real control over our platform. Is that level of knowledge deep enough? Probably not, since knowledge of the underlying metadata and structures would be very useful in helping us make sense of any query plan. Understanding the structure of an index makes the “key lookup” operator not sound like what you do when someone tapes your car key to the ceiling. So is even this level of understanding deep enough? Do we need to understand the memory architecture used to process the query? It might be a comforting level of knowledge, and will doubtless come in handy at some point, but is not strictly necessary in most cases. Beyond that lies (more or less) full knowledge of SQL language and the intricacies of every step the SQL Server engine takes to process our query. My personal theory is that, as a professional, our knowledge of a given task should extend, at a minimum, one level deeper than is strictly necessary to perform the task. Anything deeper can be left to the ridiculously smart, or obsessive, or both. As an example. tasked with storing an integer value between 0 and 99999999, it’s essential that I know that choosing an Integer over Decimal(8,0) will likely offer performance benefits. It is then useful that I also understand the value of adding a CHECK constraint, to make sure the values are valid to the desired range; and comforting that I know a little about the underlying processors, registers and computer math. Anything further, I leave to the likes of Joe Chang, whose recent blog post on the topic offers depth by the bucketful!  

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• surgemail vs Exchange

  - by Gaz

  At work we are running Surgemail. The desktop mail client is Outlook which downloads mail over POP3, and so email is stored on users desktops in PST files. Looking at the features of Surgemail compared to Exchange 2007 can anyone provide a convincing argument to change? The argument must be user related or disaster recovery related they can not be about administration of the system.

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• fail2ban Error Gentoo

  - by Mark Davidson

  Hi All I've recently setup a new VPS running Gentoo (My first time using the distro so please forgive me is this is a really easy one) and as I've done with other servers installed fail2ban. Setting it up to block the host via iptables, on too many unsuccessful logins with ssh. However I'm getting a strange error that I can't quite solve. When I start fail2ban I get these lines in the error log 2009-11-13 18:02:01,290 fail2ban.jail : INFO Jail 'ssh-iptables' started 2009-11-13 18:02:01,480 fail2ban.actions.action: ERROR iptables -N fail2ban-SSH iptables -A fail2ban-SSH -j RETURN iptables -I INPUT -p tcp --dport ssh -j fail2ban-SSH returned 100 If I try and force a ban these errors show up in the log and the host is not banned 2009-11-13 11:23:26,905 fail2ban.actions: WARNING [ssh-iptables] Ban XXX.XXX.XXX.XXX 2009-11-13 11:23:26,929 fail2ban.actions.action: ERROR iptables -n -L INPUT | grep -q fail2ban-SSH returned 100 2009-11-13 11:23:26,930 fail2ban.actions.action: ERROR Invariant check failed. Trying to restore a sane environment 2009-11-13 11:23:27,007 fail2ban.actions.action: ERROR iptables -N fail2ban-SSH iptables -A fail2ban-SSH -j RETURN iptables -I INPUT -p tcp --dport ssh -j fail2ban-SSH returned 100 2009-11-13 11:23:27,016 fail2ban.actions.action: ERROR iptables -n -L INPUT | grep -q fail2ban-SSH returned 100 2009-11-13 11:23:27,016 fail2ban.actions.action: CRITICAL Unable to restore environment My versions are as follows Linux masked 2.6.18-xen-r12 #2 SMP Wed Mar 4 11:45:03 GMT 2009 x86_64 Intel(R) Xeon(R) CPU E5504 @ 2.00GHz GenuineIntel GNU/Linux net-analyzer/fail2ban-0.8.4 net-firewall/iptables-1.4.3.2 If anyone could shead some light on these errors that would be great, I did wonder if it was a problem with iptables or some kernel modules but I can block an IP if I do. iptables -I INPUT -s 25.55.55.55 -j DROP so makes me think its something a bit more unusual. Thanks a lot in advance

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• Need to boot into chkdsk from USB on Windows netbook

  - by Gaz Davidson

  While attempting to install Ubuntu on a 32-bit Windows XP netbook, the partition resize operation failed due to inconsistencies in the NTFS filesystem (lesson learned: run chkdsk /f in Windows before trying to resize a partition in Linux). Now the installer only gives the option to replace Windows with Ubuntu, the partition can't be resized in gparted, which displays a red exclamation mark and an error log when you click it. To make matters worse, we're also unable to reboot into Windows to get at chkdsk. We get a BSoD when choosing any of the options (including the DOS recovery console thing). The netbook has no CD-ROM drive, contains no recovery image and our only connection to the Internet is via the hotspot on my mobile device. We don't have Windows recovery CDs, but we do have a USB flash drive. We have a 64-bit laptop running Ubuntu 12.04 and Windows 7 (both 64-bit). So, on to the question: Is anyone aware of a way to get into a DOS recovery console and run chkdsk from a USB disk drive, without having to pirate Windows XP or download hundreds and hundreds of megabytes of crap? If it was my device I'd just flatten it, but it isn't. Please help!

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