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  • Java Programming Help

    - by user215049
    hi, im a bit confused on this and i dont know how to solve this question that i have been asked, id be grateful if you could assist me on this question, maybe try to tell me what needs to be done, and how. the question is: Write a method called countChars which takes an InputStream as a parameter, reads the stream and returns the number of characters it contains as an int. Any IOExceptions which might occur in the method should be passed back to the method's caller. Note that the method header should show that it is possible that an exception might occur. i attempted this question with the following code: public class countChars { public int countChars(int InputStream) { return InputStream; } } and i get an error message saying : Main.java:26: cannot find symbol symbol : method countChars(java.io.InputStream) location: class Main s1 = "" + countChars(f1); ^ 1 error

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  • In yii how to access other tables fields

    - by user1636115
    I am creating project in yii framework. I am having table as- Qbquestion QbquestionOption -questionId -optionId -question -questionId -userId -option -isPublished -isAnswer In QbquestionOption controller i want to access Qbquestion tables fields. I had written quesry as- $Question=Qbquestion::model()->findAllByAttributes(array("questionId"=>$number)); where $number is some random number. When i am using its fields as= $Question-isPublished then its giving error as "trying to get access to property of non-object" Statement var_dump($Question) is showing all record and all values of Qbquestion table. So how can i access records? Please help me

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  • mysql select when matching multiple rows

    - by user1735943
    I have a project where I need to select only the users that answered to some questions in a certain way (based on a filter). The filter table (filter) looks like this question | answer Q1 | A Q2 | B The user table (answers) looks like this user | question | answer 1 | Q1 | A 1 | Q2 | D 2 | Q1 | A 2 | Q2 | B How can I select from the user table only the user(s) that match the filter? I tried "SELECT user FROM answers WHERE (question = Q1 AND answer = A) AND (question = Q2 AND answer = B)" and it doesn't work -- I get an empty result. Thank you.

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  • disk-to-disk backup without costly backup redundancy?

    - by AaronLS
    A good backup strategy involves a combination of 1) disconnected backups/snapshots that will not be affected by bugs, viruses, and/or security breaches 2) geographically distributed backups to protect against local disasters 3) testing backups to ensure that they can be restored as needed Generally I take an onsite backup daily, and an offsite backup weekly, and do test restores periodically. In the rare circumstance that I need to restore files, I do some from the local backup. Should a catastrophic event destroy the servers and local backups, then the offsite weekly tape backup would be used to restore the files. I don't need multiple offsite backups with redundancy. I ALREADY HAVE REDUNDANCY THROUGH THE USE OF BOTH LOCAL AND REMOTE BACKUPS. I have recovery blocks and par files with the backups, so I already have protection against a small percentage of corrupt bits. I perform test restores to ensure the backups function properly. Should the remote backups experience a dataloss, I can replace them with one of the local backups. There are historical offsite backups as well, so if a dataloss was not noticed for a few weeks(such as a bug/security breach/virus), the data could be restored from an older backup. By doing this, the only scenario that poses a risk to complete data loss would be one where both the local, remote, and servers all experienced a data loss in the same time period. I'm willing to risk that happening since the odds of that trifecta negligibly small, and the data isn't THAT valuable to me. So I hope I have emphasized that I don't need redundancy in my offsite backups because I have covered all the bases. I know this exact technique is employed by numerous businesses. Of course there are some that take multiple offsite backups, because the data is so incredibly valuable that they don't even want to risk that trifecta disaster, but in the majority of cases the trifecta disaster is an accepted risk. I HAD TO COVER ALL THIS BECAUSE SOME PEOPLE DON'T READ!!! I think I have justified my backup strategy and the majority of businesses who use offsite tape backups do not have any additional redundancy beyond what is mentioned above(recovery blocks, par files, historical snapshots). Now I would like to eliminate the use of tapes for offsite backups, and instead use a backup service. Most however are extremely costly for $/gb/month storage. I don't mind paying for transfer bandwidth, but the cost of storage is way to high. All of them advertise that they maintain backups of the data, and I imagine they use RAID as well. Obviously if you were using them to host servers this would all be necessary, but for my scenario, I am simply replacing my offsite backups with such a service. So there is no need for RAID, and absolutely no value in another layer of backups of backups. My one and only question: "Are there online data-storage/backup services that do not use redundancy or offer backups(backups of my backups) as part of their packages, and thus are more reasonably priced?" NOT my question: "Is this a flawed strategy?" I don't care if you think this is a good strategy or not. I know it pretty standard. Very few people make an extra copy of their offsite backups. They already have local backups that they can use to replace the remote backups if something catastrophic happens at the remote site. Please limit your responses to the question posed. Sorry if I seem a little abrasive, but I had some trolls in my last post who didn't read my requirements nor my question, and were trying to go off answering a totally different question. I made it pretty clear, but didn't try to justify my strategy, because I didn't ask about whether my strategy was justifyable. So I apologize if this was lengthy, as it really didn't need to be, but since there are so many trolls here who try to sidetrack questions by responding without addressing the question at hand.

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  • Determining cause of high NFS/IO utilization without iotop

    - by Matt
    I have a server that is doing an NFSv4 export for user's home directories. There are roughly 25 users (mostly developers/analysts) and about 40 servers mounting the home directory export. Performance is miserable, with users often seeing multi-second lags for simple commands (like ls, or writing a small text file). Sometimes the home directory mount completely hangs for minutes, with users getting "permission denied" errors. The hardware is a Dell R510 with dual E5620 CPUs and 8 GB RAM. There are eight 15k 2.5” 600 GB drives (Seagate ST3600057SS) configured in hardware RAID-6 with a single hot spare. RAID controller is a Dell PERC H700 w/512MB cache (Linux sees this as a LSI MegaSAS 9260). OS is CentOS 5.6, home directory partition is ext3, with options “rw,data=journal,usrquota”. I have the HW RAID configured to present two virtual disks to the OS: /dev/sda for the OS (boot, root and swap partitions), and /dev/sdb for the home directories. What I find curious, and suspicious, is that the sda device often has very high utilization, even though it only contains the OS. I would expect this virtual drive to be idle almost all the time. The system is not swapping, according to "free" and "vmstat". Why would there be major load on this device? Here is a 30-second snapshot from iostat: Time: 09:37:28 AM Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 0.00 44.09 0.03 107.76 0.13 607.40 11.27 0.89 8.27 7.27 78.35 sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda2 0.00 44.09 0.03 107.76 0.13 607.40 11.27 0.89 8.27 7.27 78.35 sdb 0.00 2616.53 0.67 157.88 2.80 11098.83 140.04 8.57 54.08 4.21 66.68 sdb1 0.00 2616.53 0.67 157.88 2.80 11098.83 140.04 8.57 54.08 4.21 66.68 dm-0 0.00 0.00 0.03 151.82 0.13 607.26 8.00 1.25 8.23 5.16 78.35 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 0.67 2774.84 2.80 11099.37 8.00 474.30 170.89 0.24 66.84 dm-3 0.00 0.00 0.67 2774.84 2.80 11099.37 8.00 474.30 170.89 0.24 66.84 Looks like iotop is the ideal tool to use to sniff out these kinds of issues. But I'm on CentOS 5.6, which doesn't have a new enough kernel to support that program. I looked at Determining which process is causing heavy disk I/O?, and besides iotop, one of the suggestions said to do a "echo 1 /proc/sys/vm/block_dump". I did that (after directing kernel messages to tempfs). In about 13 minutes I had about 700k reads or writes, roughly half from kjournald and the other half from nfsd: # egrep " kernel: .*(READ|WRITE)" messages | wc -l 768439 # egrep " kernel: kjournald.*(READ|WRITE)" messages | wc -l 403615 # egrep " kernel: nfsd.*(READ|WRITE)" messages | wc -l 314028 For what it's worth, for the last hour, utilization has constantly been over 90% for the home directory drive. My 30-second iostat keeps showing output like this: Time: 09:36:30 PM Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 0.00 6.46 0.20 11.33 0.80 71.71 12.58 0.24 20.53 14.37 16.56 sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda2 0.00 6.46 0.20 11.33 0.80 71.71 12.58 0.24 20.53 14.37 16.56 sdb 137.29 7.00 549.92 3.80 22817.19 43.19 82.57 3.02 5.45 1.74 96.32 sdb1 137.29 7.00 549.92 3.80 22817.19 43.19 82.57 3.02 5.45 1.74 96.32 dm-0 0.00 0.00 0.20 17.76 0.80 71.04 8.00 0.38 21.21 9.22 16.57 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 687.47 10.80 22817.19 43.19 65.48 4.62 6.61 1.43 99.81 dm-3 0.00 0.00 687.47 10.80 22817.19 43.19 65.48 4.62 6.61 1.43 99.82

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  • ESXI guests not using available CPU resources

    - by Alan M
    I have a VMWare ESXI 5.0.0 (it's a bit old, I know) host with three guest VMs on it. For reasons unknown, the guests will not use much of the availble CPU resources. I have all three guests in a single pool, with the hosts all configured to use the same amount of resource shares, so they're basically 33% each. The three guests are basically identically configured as far as their VM resources go. So the problem is, even when the guests are performing what should be very 'busy' activitites, such as at bootup, the actual host CPU consumed is something tiny, like 33mhz, when seen via vSphere console's "Virtual Machines" tab when viewing properties for the pool. And of course, the performance of the guest VMs is terrible. The host has plenty of CPU to spare. I've tried tinkering with individual guest VM resource settings; cranking up the reservation, etc. No matter. The guests just refuse to make use of the abundant CPU available to them, and insist on using a sliver of the available resources. Any suggestions? Update after reading various comments below Per the suggestions below, I did remove the guests from the application pool; this didn't make any difference. I do understand that the guests are not going to consume resources they do not need. I have tried to do a remote perfmon on the guest which is experiencing long boot times, but I cannot connect to the guest remotely with perfmon (guest is w2k8r2 server). Host graphs for CPU, Mem, Disk are basically flatlining; very little demand. Same is true for the guest stats; while the guest itself seems to be crawling, the guest resource graphing shows very little activity across CPU, Mem, Disk. Host is a Dell PowerEdge 2900, has 2 physical CPU,20gb RAM. (it's a test/dev environment using surplus gear) Guest1 has: VM ver. 7, 2vCPU, 4gb RAM, 140gb storage which lives on a RAID-5 array on the host. Guest2 has: VM ver. 7, 2vCPU, 4gb RAM, 140gb storage which lives on a RAID-5 array on the host. Guest3 has: VM ver. 7, 1vCPU, 2gb RAM, 2tb storage which lives on a RAID-5 ISCSI NAS box Perhaps I am making a false assumption that if a guest has a demand for CPU (e.g. Windows Task Manager shows 100% CPU), the host would supply the guest with more CPU (mem, disk) on demand. Another Update After checking the stats, it would appear that the host is indeed not busy at all, neither is the guest. I believe I have a good idea on the issue, though; a messed-up VMWare Tools install. The guest has VMware Tools on it, but the host says it does not. VMWare Tools refuses to uninstall, refuses to be upgraded, refuses to be recognized. While I cannot say with authority, this would appear to be something worth investigation. I do not know the origin of the guest itself, nor the specifics on the original VMWare Tools install. Following various bits of googling, I did come up with a few suggestions that went nowhere. To that end, I was going to delete this question, but was prompted not to do so since so many folks answered. My suspicion right now is; the problem truly is the guest; the guest is not making a demand on the host, and as a natural result, the host is treating the guest accordingly. My Final Update I am 99% certain the guest VM had something fundamentally wrong with it re VMWare Tools. I created a clone of a different VM with a near-identical OS config, but a properly working install of VMWare tools. The guest runs just great, and takes up it's allotment of resources when it needs to; e.g. it eats up about 850mhz CPU during startup, then ticks down to idle once the guest OS is stable.

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  • File server share access intermittent/slow/machine unstable: win2k8r2

    - by Jack B.
    I have a file server running Win2k8R2 on an older HP DL380G4. It has nothing set up on it other than file sharing. All drivers/firmware/updates installed. The file server is used as a dump for a bunch of test machines - so essentially a lot of small files are being written to it. It was working fine until it started showing the following symptoms: Shares became either very slow/intermittent or could not access them at all. Logging in the the server, you could use it like normal but windows would start freezing and eventually you had to hard reboot it because nothing was responsive. After rebooting, it would work fine for 20min-2hours and then degrade into this broken state again. Some info after investigation: HP Raid Config utility shows the Raid array as functioning properly (RAID5 btw). Event log shows a bunch of DoS attacks from the test machines, saying it has disconnected the connection a. AFAIK (not part of my job) the test machines haven't changed the way they log information to this server or the amount of them hasn't increased. b. Nothing is infected, this server was scanned fully, and the test machines are re-imaged almost daily. Nothing in performance monitor shows as anything being pegged at maximum (CPU/HD/Network/RAM) I installed MS Network Monitor and it is showing a lot of traffic The server was using one gigabit Ethernet connection, I connected the second one as well with the same results. Forgot to add - one of the commonly written to dirs on the share has over 16k subdirs in it, with a crapton of small files within those dirs. Some of the OS instability was slow access to the drive which has this directory - perfmon doesn't show much activity on the HD though so I'm not sure if this crowded dir is the cause. Here is one important fact: I ran into this issue 2-3 months ago, couldn't figure it out, but I had a spare identical machine so I swapped them out (thought it was related to the machine), and now I have the same issue. Also, the computer will be stable if I turn off file sharing. So is the server just getting DoS'd by the test machines? I've never dealt with such an issue. Is instability in the server's OS common when getting DoS'd? Is there anything I can do to confirm this before telling the owners of the test machines to optimize their traffic? (I'm not sure what they'll be able to do). Is there something within Win2k8R2 that can balance the traffic across the two NICs? Any help would be appreciated. Update: Another thought - the drive with the share is RAID5 across 6 SCSI320 300GB HDs. They are near full capacity about 100GB from 1TB left. Could the amount of tiny files could be causing some weirdness with the parity in this array? I think I've read something about this in the past but I'm no expert on RAID.

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  • WNDR3700 Router + Cisco SG200-08 + LACP + Dual Uplink

    - by kobaltz
    Background I have a storage server that has several virtual machine images stored on them. I would store them locally, but I have limited space on my desktop (using SSD storage). I would like to increase the bandwidth between the desktop and the storage server by using two NICs on each computer. My original configuration allowed about 55MBps between the desktop and storage server. This storage server also has several TBs of documents, pictures, movies, vms, and ISO/programs. The storage server has 8 1.5TB hard drives in a RAID 10 configuration with a hardware RAID controller. The benchmarks on the RAID 10 are about 300MBps. Configuration In short, I am trying to bridge my switch and router. The switch is a small 8 port Cisco smart switch that supports 802.3ad LACP. I have two computers plugged into the switch, each with 2 Intel Gigabit NICs. The first computer is a Windows 7 machine that has the Intel ANS software installed. I have LACP configured with the computer and now show 3 NICs (2 Physical + 1 TEAM Virtual @ 2Gbps). It looks like this computer is configured correctly. I trunked the two ports that this computer is plugged into with the switch's web interface. The second computer is a homebrew storage box running debian. I also have the bonding enabled on this machine and the switch configured with LACP. Without having the WNDR3700 router in the picture yet, I am able to communicate between the Windows 7 machine and the debian box since they both have static IP addresses. With LACP enabled on both machines I am getting about 106-108MBps speeds. Issue I plug in a network cable from the switch into the router and enable DHCP on the desktop. I saw no need to have a static address on the desktop. My transfer rates are still from 106MBps-108MBps. While this is still a boost, I am trying to figure out how to get about 140-180MBps. I am thinking that I need to increase the bandwidth from the router to the switch. My switch allows 4 groups for port trunking. I plugged in a second network cable from the router to the switch. My question is, what is the proper way to fix this issue. Should I port trunk the two ports that are going from the switch to the router? Keep in mind that the router is a WNDR3700 and is unsure whether or not it supports LACP. I do have OpenWRT installed on the router, but it still wasn't clear in any documentation that I found if it supported 802.3ad LACP standards. I am also wondering if there needs to be anything changed within the Cisco settings. [Edit] - Corrected some numbers, wasn't really paying attention. It looks like the speeds though at least two NICs are bonded with LACP is still reaching the max bandwidth of one port. Is there a way to configure the switch so that I can increase this bandwidth? Also, on the storage server, I had a couple of extra NICs laying around and threw them on there as well. Another EDIT and More Findings I happened to look at the traffic of each individual NIC and think that I see the problem. I tested with a simple transfer for a 4GB file. I noticed that only one of the NICs was taking the load of the traffic. I then copied the file back to the Storage Server and noticed that the other NIC was sending out the traffic. I have 802.3ad LACP enabled on the two NICs and I see that it gets enabled dynamically on the switch's interface. Should I be using Static Link Aggregation?

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  • File server share access intermittent/slow/machine unstable: win2k8r2

    - by Jack B.
    I have a file server running Win2k8R2 on an older HP DL380G4. It has nothing set up on it other than file sharing. All drivers/firmware/updates installed. The file server is used as a dump for a bunch of test machines - so essentially a lot of small files are being written to it. It was working fine until it started showing the following symptoms: Shares became either very slow/intermittent or could not access them at all. Logging in the the server, you could use it like normal but windows would start freezing and eventually you had to hard reboot it because nothing was responsive. After rebooting, it would work fine for 20min-2hours and then degrade into this broken state again. Some info after investigation: HP Raid Config utility shows the Raid array as functioning properly (RAID5 btw). Event log shows a bunch of DoS attacks from the test machines, saying it has disconnected the connection a. AFAIK (not part of my job) the test machines haven't changed the way they log information to this server or the amount of them hasn't increased. b. Nothing is infected, this server was scanned fully, and the test machines are re-imaged almost daily. Nothing in performance monitor shows as anything being pegged at maximum (CPU/HD/Network/RAM) I installed MS Network Monitor and it is showing a lot of traffic The server was using one gigabit Ethernet connection, I connected the second one as well with the same results. Forgot to add - one of the commonly written to dirs on the share has over 16k subdirs in it, with a crapton of small files within those dirs. Some of the OS instability was slow access to the drive which has this directory - perfmon doesn't show much activity on the HD though so I'm not sure if this crowded dir is the cause. Here is one important fact: I ran into this issue 2-3 months ago, couldn't figure it out, but I had a spare identical machine so I swapped them out (thought it was related to the machine), and now I have the same issue. Also, the computer will be stable if I turn off file sharing. So is the server just getting DoS'd by the test machines? I've never dealt with such an issue. Is instability in the server's OS common when getting DoS'd? Is there anything I can do to confirm this before telling the owners of the test machines to optimize their traffic? (I'm not sure what they'll be able to do). Is there something within Win2k8R2 that can balance the traffic across the two NICs? Any help would be appreciated. Update: Another thought - the drive with the share is RAID5 across 6 SCSI320 300GB HDs. They are near full capacity about 100GB from 1TB left. Could the amount of tiny files could be causing some weirdness with the parity in this array? I think I've read something about this in the past but I'm no expert on RAID.

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  • File server share access intermittent/slow/machine unstable: win2kr2

    - by Jack B.
    I have a file server running Win2k8R2 on an older HP DL380G4. It has nothing set up on it other than file sharing. All drivers/firmware/updates installed. The file server is used as a dump for a bunch of test machines - so essentially a lot of small files are being written to it. It was working fine until it started showing the following symptoms: Shares became either very slow/intermittent or could not access them at all. Logging in the the server, you could use it like normal but windows would start freezing and eventually you had to hard reboot it because nothing was responsive. After rebooting, it would work fine for 20min-2hours and then degrade into this broken state again. Some info after investigation: HP Raid Config utility shows the Raid array as functioning properly (RAID5 btw). Event log shows a bunch of DoS attacks from the test machines, saying it has disconnected the connection a. AFAIK (not part of my job) the test machines haven't changed the way they log information to this server or the amount of them hasn't increased. b. Nothing is infected, this server was scanned fully, and the test machines are re-imaged almost daily. Nothing in performance monitor shows as anything being pegged at maximum (CPU/HD/Network/RAM) I installed MS Network Monitor and it is showing a lot of traffic The server was using one gigabit Ethernet connection, I connected the second one as well with the same results. Forgot to add - one of the commonly written to dirs on the share has over 16k subdirs in it, with a crapton of small files within those dirs. Some of the OS instability was slow access to the drive which has this directory - perfmon doesn't show much activity on the HD though so I'm not sure if this crowded dir is the cause. Here is one important fact: I ran into this issue 2-3 months ago, couldn't figure it out, but I had a spare identical machine so I swapped them out (thought it was related to the machine), and now I have the same issue. Also, the computer will be stable if I turn off file sharing. So is the server just getting DoS'd by the test machines? I've never dealt with such an issue. Is instability in the server's OS common when getting DoS'd? Is there anything I can do to confirm this before telling the owners of the test machines to optimize their traffic? (I'm not sure what they'll be able to do). Is there something within Win2k8R2 that can balance the traffic across the two NICs? Any help would be appreciated. Update: Another thought - the drive with the share is RAID5 across 6 SCSI320 300GB HDs. They are near full capacity about 100GB from 1TB left. Could the amount of tiny files could be causing some weirdness with the parity in this array? I think I've read something about this in the past but I'm no expert on RAID.

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  • FTP script needs blank line

    - by Ones and Zeroes
    I am trying to determine the reason for some FTP servers requiring a blank line in the script as follows: open server.com username ftp_commands bye Refer to blank line required after username credentials. Example from: FTP from batch file another reference to the same: http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.ibm.as400.misc/2008-05/msg00227.html Also discussed here: archive.midrange.com/midrange-l/200601/msg00048.html "The behavior I'm observing is the same as if I didn't specify the password to login." with an answer referring to our same fix... archive.midrange.com/midrange-l/200601/msg00053.html and archive.midrange.com/midrange-l/200601/msg00065.html Note: It is my experience that FTP questions attract uncouth responses. Admittedly FTP is outdated, but many clients still have legacy systems, which they cannot upgrade or replace. The reason thereof should not be discussed here. The intention of this question is to invite a positive response. Please do not respond if you disagree with the above. If you have never encountered this same issue, please do not respond. I suspect this may be limited to FTP scripts executed from Windows machines, but have been told that this happens often and with many different servers. My specific interest is to understand what may cause this as I have a real world example of a production system suddenly requiring this as a workaround fix, after running for many years without issue. The server belongs to a third party who claims no change on their end. Server details unknown and cannot be determined. Any help or encouragement from someone who has come across the same, would be appreciated. ps. Sorry for the many words and references to painful responses, but I have asked similar questions on serverfault and elsewhere and unfortunately got back kneejerk responses to FTP and respondents debating the validity of the question. I would truly not ask, or re-post this question online if I had a better understanding of the issue. I know of people who have seen this issue, but don't know what causes it. I am wary that this question would again turn into another irrelevant discussion. Please, I ask very nicely: Please do not respond if you have not encountered a similar issue. FURTHER EDIT: Please do not suggest changing the product. The problem is not the blank line requirement. We know this fixes the issue. The problem is not being able to explain the reason for the blank line in the first place. Slight difference, but a critical point to note wrt the answering of this question.

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  • SQL SERVER – How to See Active SQL Server Connections For Database

    - by Pinal Dave
    Another question received via email - “How do I I know which user is connected to my database with how many connection?” Here is the script which will give us answer to the question. SELECT DB_NAME(dbid) AS DBName, COUNT(dbid) AS NumberOfConnections, loginame FROM    sys.sysprocesses GROUP BY dbid, loginame ORDER BY DB_NAME(dbid) Here is the resultset: Reference: Pinal Dave (http://blog.SQLAuthority.com)Filed under: PostADay, SQL, SQL Authority, SQL DMV, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Racing MMO for Linux - 2D or 3D - Massively Multiplayer Online Racing Games for Linux

    - by Paulocoghi
    I really like multiplayer racing games, like Need for Speed World or similar. I wonder if there is any MMO racing game for Linux (2D or 3D). Browser-based games are also accepted. Note: I tried this question in the Gaming Q&A of StackExchange (see link below), but one user said that my question was off-topic. http://gaming.stackexchange.com/questions/16329/racing-mmo-for-linux-2d-or-3d-massively-multiplayer-online-racing-games

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  • How to represent a Rubik's Cube in a data structure

    - by Mel
    I am just curious, how will you guys create a data structure for a rubik's cube with X number of sides. Things to consider: - the cube can be of any size - it is a rubik's cube! so layers can be rotated (in all three axes) and a plus question: using the data structure, how can we know if a certain cube in a certain state is solvable? I have been struggling with this question my self and haven't quite found the answer yet.

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  • An XEvent a Day (16 of 31) – How Many Checkpoints are Issued During a Full Backup?

    - by Jonathan Kehayias
    This wasn’t my intended blog post for today, but last night a question came across #SQLHelp on Twitter from Varun ( Twitter ). #sqlhelp how many checkpoints are issued during a full backup? The question was answered by Robert Davis (Blog|Twitter) as: Just 1, at the very start. RT @ 1sql : #sqlhelp how many checkpoints are issued during a full backup? This seemed like a great thing to test out with Extended Events so I ran through the available Events in SQL Server 2008, and the only Event related...(read more)

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  • 1 Million IOPS

    - by GrumpyOldDBA
    As a keen follower of storage performance I couldn't help but be drawn to this article in The Register http://www.theregister.co.uk/2010/04/14/lsi_million_iops/ this morning. I gave my 5 year old laptop a new lease of life with a SSD and in combination with the old drive made external managed to reduce the time of a demo query from 50 odd mins down to 6 mins. I also have 4 Silicon Power 32GB SSDs set up as a raid 0 on my home server, an overblown PC. http://www.futurestorage.co.uk/index.asp?selmanuf...(read more)

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  • Why Most Web Services Don’t Use End-to-End Encryption

    - by Chris Hoffman
    Recent revelations about government surveillance have raised the question: why don’t cloud services encrypt your data? Well, they generally do encrypt your data, but they have the key so they can decrypt it any time they like. The real question is: Why don’t web services encrypt and decrypt your data locally, so that it’s stored in an encrypted form no one can snoop on? LastPass does this with your password database, after all.    

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  • Do unit tests sometimes break encapsulation?

    - by user1288851
    I very often hear the following: "If you want to test private methods, you'd better put that in another class and expose it." While sometimes that's the case and we have a hiding concept inside our class, other times you end up with classes that have the same attributes (or, worst, every attribute of one class become a argument on a method in the other class) and exposes functionality that is, in fact, implementation detail. Specially on TDD, when you refactor a class with public methods out of a previous tested class, that class is now part of your interface, but has no tests to it (since you refactored it, and is a implementation detail). Now, I may be not finding an obvious better answer, but if my answer is the "correct", that means that sometimes writting unit tests can break encapsulation, and divide the same responsibility into different classes. A simple example would be testing a setter method when a getter is not actually needed for anything in the real code. Please when aswering don't provide simple answers to specific cases I may have written. Rather, try to explain more of the generic case and theoretical approach. And this is neither language specific. Thanks in advance. EDIT: The answer given by Matthew Flynn was really insightful, but didn't quite answer the question. Altough he made the fair point that you either don't test private methods or extract them because they really are other concern and responsibility (or at least that was what I could understand from his answer), I think there are situations where unit testing private methods is useful. My primary example is when you have a class that has one responsibility but the output (or input) that it gives (takes) is just to complex. For example, a hashing function. There's no good way to break a hashing function apart and mantain cohesion and encapsulation. However, testing a hashing function can be really tough, since you would need to calculate by hand (you can't use code calculation to test code calculation!) the hashing, and test multiple cases where the hash changes. In that way (and this may be a question worth of its own topic) I think private method testing is the best way to handle it. Now, I'm not sure if I should ask another question, or ask it here, but are there any better way to test such complex output (input)? OBS: Please, if you think I should ask another question on that topic, leave a comment. :)

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  • Should I refer to browser-based games as HTML5 games or Javascript games?

    - by Bane
    First of all, I know that there are alternatives to both HTML5 and Javascript, but I worded the question so generally ("browser-based") because if I had said "HTML5" or "Javascript" games that would already imply an answer to the question. When writing wiki posts or discussing, I usually call these games "HTML5/Javascript" games. They are written in Javascript, using the new HTML5 technology. What is the proper way to call them: HTML5 or Javascript games? I see that most people opt for HTML5, why?

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  • SQL SERVER – A Quick Look at Logging and Ideas around Logging

    - by pinaldave
    This blog post is written in response to the T-SQL Tuesday post on Logging. When someone talks about logging, personally I get lots of ideas about it. I have seen logging as a very generic term. Let me ask you this question first before I continue writing about logging. What is the first thing comes to your mind when you hear word “Logging”? Now ask the same question to the guy standing next to you. I am pretty confident that you will get  a different answer from different people. I decided to do this activity and asked 5 SQL Server person the same question. Question: What is the first thing comes to your mind when you hear the word “Logging”? Strange enough I got a different answer every single time. Let me just list what answer I got from my friends. Let us go over them one by one. Output Clause The very first person replied output clause. Pretty interesting answer to start with. I see what exactly he was thinking. SQL Server 2005 has introduced a new OUTPUT clause. OUTPUT clause has access to inserted and deleted tables (virtual tables) just like triggers. OUTPUT clause can be used to return values to client clause. OUTPUT clause can be used with INSERT, UPDATE, or DELETE to identify the actual rows affected by these statements. Here are some references for Output Clause: OUTPUT Clause Example and Explanation with INSERT, UPDATE, DELETE Reasons for Using Output Clause – Quiz Tips from the SQL Joes 2 Pros Development Series – Output Clause in Simple Examples Error Logs I was expecting someone to mention Error logs when it is about logging. The error log is the most looked place when there is any error either with the application or there is an error with the operating system. I have kept the policy to check my server’s error log every day. The reason is simple – enough time in my career I have figured out that when I am looking at error logs I find something which I was not expecting. There are cases, when I noticed errors in the error log and I fixed them before end user notices it. Other common practices I always tell my DBA friends to do is that when any error happens they should find relevant entries in the error logs and document the same. It is quite possible that they will see the same error in the error log  and able to fix the error based on the knowledge base which they have created. There can be many different kinds of error log files exists in SQL Server as well – 1) SQL Server Error Logs 2) Windows Event Log 3) SQL Server Agent Log 4) SQL Server Profile Log 5) SQL Server Setup Log etc. Here are some references for Error Logs: Recycle Error Log – Create New Log file without Server Restart SQL Error Messages Change Data Capture I got surprised with this answer. I think more than the answer I was surprised by the person who had answered me this one. I always thought he was expert in HTML, JavaScript but I guess, one should never assume about others. Indeed one of the cool logging feature is Change Data Capture. Change Data Capture records INSERTs, UPDATEs, and DELETEs applied to SQL Server tables, and makes a record available of what changed, where, and when, in simple relational ‘change tables’ rather than in an esoteric chopped salad of XML. These change tables contain columns that reflect the column structure of the source table you have chosen to track, along with the metadata needed to understand the changes that have been made. Here are some references for Change Data Capture: Introduction to Change Data Capture (CDC) in SQL Server 2008 Tuning the Performance of Change Data Capture in SQL Server 2008 Download Script of Change Data Capture (CDC) CDC and TRUNCATE – Cannot truncate table because it is published for replication or enabled for Change Data Capture Dynamic Management View (DMV) I like this answer. If asked I would have not come up with DMV right away but in the spirit of the original question, I think DMV does log the data. DMV logs or stores or records the various data and activity on the SQL Server. Dynamic management views return server state information that can be used to monitor the health of a server instance, diagnose problems, and tune performance. One can get plethero of information from DMVs – High Availability Status, Query Executions Details, SQL Server Resources Status etc. Here are some references for Dynamic Management View (DMV): SQL SERVER – Denali – DMV Enhancement – sys.dm_exec_query_stats – New Columns DMV – sys.dm_os_windows_info – Information about Operating System DMV – sys.dm_os_wait_stats Explanation – Wait Type – Day 3 of 28 DMV sys.dm_exec_describe_first_result_set_for_object – Describes the First Result Metadata for the Module Transaction Log Impact Detection Using DMV – dm_tran_database_transactions Log Files I almost flipped with this final answer from my friend. This should be probably the first answer. Yes, indeed log file logs the SQL Server activities. One can write infinite things about log file. SQL Server uses log file with the extension .ldf to manage transactions and maintain database integrity. Log file ensures that valid data is written out to database and system is in a consistent state. Log files are extremely useful in case of the database failures as with the help of full backup file database can be brought in the desired state (point in time recovery is also possible). SQL Server database has three recovery models – 1) Simple, 2) Full and 3) Bulk Logged. Each of the model uses the .ldf file for performing various activities. It is very important to take the backup of the log files (along with full backup) as one never knows when backup of the log file come into the action and save the day! How to Stop Growing Log File Too Big Reduce the Virtual Log Files (VLFs) from LDF file Log File Growing for Model Database – model Database Log File Grew Too Big master Database Log File Grew Too Big SHRINKFILE and TRUNCATE Log File in SQL Server 2008 Can I just say I loved this month’s T-SQL Tuesday Question. It really provoked very interesting conversation around me. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Optimization, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Storage Configuration

    - by jchang
    Storage performance is not inherently complicated subject. The concepts are relatively simple. In fact, scaling storage performance is far easier compared with the difficulties encounters in scaling processor performance in NUMA systems. Storage performance is achieved by properly distributing IO over: 1) multiple independent PCI-E ports (system memory and IO bandwith is key) 2) multiple RAID controllers or host bus adapters (HBAs) 3) multiple storage IO channels (SAS or FC, complete path) most importantly,...(read more)

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  • The Basics of Desktop Data Recovery

    Desktop data recovery is an important part of computer repairs, as it is pretty common for a hard drive or server RAID to fail and lose major amounts of data. With desktops especially, it is sometime... [Author: Richard Cuthbertson - Computers and Internet - April 07, 2010]

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  • Uses for Types of Data Recovery Services

    There are several different types of data recovery services, including hard drive, server raid, and smart media recovery. What makes things tricky is to know when to use which service, and how to kno... [Author: Richard Cuthbertson - Computers and Internet - April 08, 2010]

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  • Storage Configuration

    - by jchang
    Storage performance is not inherently complicated subject. The concepts are relatively simple. In fact, scaling storage performance is far easier compared with the difficulties encounters in scaling processor performance in NUMA systems. Storage performance is achieved by properly distributing IO over: 1) multiple independent PCI-E ports (system memory and IO bandwith is key) 2) multiple RAID controllers or host bus adapters (HBAs) 3) multiple storage IO channels (SAS or FC, complete path) most importantly,...(read more)

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  • What issues tend to arise when working with HL7 messages?

    - by Ethel Evans
    I'm testing a product for health care businesses, and we're working with HL7 messages. I saw people groaning on another question about the issues with HL7 but not mentioning specifics. Can someone give me some ideas of what issues or classes of problems we should specifically be looking for? We are using some well-used libraries for the parsing. If specifics about these or what we're doing would be helpful please let me know in the comments and I'll add to the question if I can.

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