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  • Routing with VPN and asymmetric communication

    - by Louis
    I'm stumbling on a problem that requires your advice. Keywords : networking, route, openVPN Problem : I have a local network with several physical servers and VMs. These machines have ip's in the range 10.10.x.x. I can access these machines from the Internet with the help of openVPN. These machines can : access each other within the local 10.10.x.x subnet access the Internet via the VPN can themselves be accessed (via SSH) from the Internet via the VPN. There is one machine however that behaves strangely and I don't know why. I can SSH into this machine from anywhere via SSH and I can also PING it from anywhere (including the Internet). However from this machine (i.e. when logged into it) I cannot access the Internet or ping machines outside the local network. In other words it will not go beyond the VPN. My question is why? Here are some technical details: The machine's Network Config (running Debian 6.0.3): allow-hotplug eth0 iface eth0 inet static address 10.10.10.200 netmask 255.255.0.0 network 10.10.10.0 broadcast 10.10.10.255 gateway 10.10.10.200 The machine's Routing : Destination Gateway Genmask Flags MSS Window irtt Iface 127.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 lo 10.10.0.0 10.10.10.250 255.255.0.0 UG 0 0 0 eth0 10.10.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0 0.0.0.0 10.10.10.250 0.0.0.0 UG 0 0 0 eth0 0.0.0.0 10.10.10.200 0.0.0.0 UG 0 0 0 eth0 The VPN's Network Config (running Debian 6.0.3): # This is the local network interface auto eth1 allow-hotplug eth1 iface eth1 inet static address 10.10.10.250 netmask 255.255.0.0 broadcast 10.10.10.255 gateway 10.10.10.250 The VPN's routing table Destination Gateway Genmask Flags MSS Window irtt Iface 10.10.0.0 0.0.0.0 255.255.255.0 U 0 0 0 tun0 private 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.10.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 0.0.0.0 10.10.10.250 0.0.0.0 UG 0 0 0 eth1 0.0.0.0 private 0.0.0.0 UG 0 0 0 eth0 net.ipv4.ip_forward = 1 on both machines. there are no iptables set anywhere. Thanks in advance for any feedback.

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  • Trouble installing Windows Embedded Standard 2009

    - by Tim
    Getting the following error when attempting to install: Error attempting to create the destination file: C:\Windows Embedded Data\Repositories\{25C88912-9870-4686-97CE-8244C A1B0DAB}.CAB. System error code: 5 Code 5 looks to be an "Access denied" issue. Not sure if this is a generic Windows error, or specific to this install. Any insight is appreciated! -Tim

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  • Bootable backup of a Mac without an HFS+ disk?

    - by marienbad
    How can I make a bootable backup of my Mac's internal hard drive to be restored using Disk Utility, without formatting my external destination drive as HFS+ (it's FAT32, of course)? Time Machine and SuperDuper both require that the volume where the backup is saved be HFS+ formatted. This looks helpful: http://developer.apple.com/macosx/backuponmacosx.html But it doesn't explain how to use FAT32 disk.

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  • Conflicting ip routes with local table on attaching a virtual network interface

    - by user1071840
    I have an EC2 instance with these ip rules: $ sudo ip rule show 0: from all lookup local 32766: from all lookup main 32767: from all lookup default I can attach an elastic network interface to it with a private IP. Say the IP of my machine is 10.1.3.12 and the IP of the interface is 10.1.1.190. As soon as I attach the interface to my machine a new entry is added to the routing policy and local routing table: sudo ip rule show 0: from all lookup local 32765: from 10.1.1.190 lookup 10003 32766: from all lookup main 32767: from all lookup default $ sudo ip route show table local broadcast 10.1.1.0 dev eth3 proto kernel scope link src 10.1.1.190 local 10.1.1.190 dev eth3 proto kernel scope host src 10.1.1.190 broadcast 10.1.1.255 dev eth3 proto kernel scope link src 10.1.1.190 broadcast 10.1.3.0 dev eth0 proto kernel scope link src 10.1.3.12 local 10.1.3.12 dev eth0 proto kernel scope host src 10.1.3.12 broadcast 10.1.3.255 dev eth0 proto kernel scope link src 10.1.3.12 broadcast 127.0.0.0 dev lo proto kernel scope link src 127.0.0.1 local 127.0.0.0/8 dev lo proto kernel scope host src 127.0.0.1 local 127.0.0.1 dev lo proto kernel scope host src 127.0.0.1 broadcast 127.255.255.255 dev lo proto kernel scope link src 127.0.0.1 I can send traffic to this ENI directly from a host that can have the same IP as the host the ENI is attached to. This is where the problem starts. I ran tcpdump on the port in question and saw multiple SYNs going to the ENI with src '10.1.3.12' and destination '10.1.1.190' but didn't see even a single ACK. In my understanding if ACKs were being sent from the ENI they'd have destination as 10.1.3.12 i.e. the same as the local machine's IP and such packets will now be routed as local packets matching local routing policy: local 10.1.3.12 dev eth0 proto kernel scope host src 10.1.3.12 I'd like to send all the packets originating from 10.1.1.190 (my ENI) to go back on the same interface i.e. eth3 in this case. Contents of the nee table 10003 are: $ sudo ip route show table 10003 default via 10.1.1.1 dev eth3 I think I can do the following: I don't know if its possible but probably decrease the priority of local table so the packets match the table 10003. Use iptables to mangle these packets and update the local table route to include the mark information But I'm not sure if these are the right approaches.

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  • forward outbound traffic rule

    - by Claudiu
    I am trying to forward the outbound traffic to another server. Current rule is: /sbin/iptables -A OUTPUT -p tcp -s localhost -o 91.xxx.xxx.xxx --dport 65000:65010 -j ACCEPT but when I do a iptables -L, the rule its showed like this: ACCEPT tcp -- localhost.localdomain anywhere tcp dpts:65000:65010 So I guess my rule is bad written since the "destination" column shows "anywhere" Can you help me with this?

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  • iptables rule for forwarding outbound traffic

    - by Claudiu
    I am trying to forward the outbound traffic to another server. Current rule is: /sbin/iptables -A OUTPUT -p tcp -s localhost -o 91.xxx.xxx.xxx --dport 65000:65010 -j ACCEPT but when I do a iptables -L, the rule its showed like this: ACCEPT tcp -- localhost.localdomain anywhere tcp dpts:65000:65010 So I guess my rule is bad written since the "destination" column shows "anywhere" Can you help me with this?

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  • Backup with bash and rsync...

    - by Roger
    Is there a way to auto-rename an existing file on the receiver? For example: if filename already exists, it auto-rename filename to something like filename_001, filename_002 and so on.... So far all I have is this: $ rsync -rh --progress --stats --exclude '.thumb' \ --update --perms /origin /destination By the way, I know rsync has --ignore-existing to "skip updating files that exist on receiver", but I guess what I need would be something like --rename-existing.

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  • PsExec Couldn't access Windows cannot find the network path

    - by Navan
    Hi , I given the below cmd using PsExec v1.96 psexec -u ADMIN_USER_NAME -p ADMIN_PWD I got the below error. Couldn't access Windows cannot find the network path. Verify that the network path is correct an d the destination computer is not busy or turned off. If Windows still cannot fi nd the network path, contact your network administrator. Thanks, Navan

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  • Cisco - Zone Policy Actions (pass, inspect, drop, log) - What is the difference?

    - by Jonathan Rioux
    Have these commands for instance: policy-map type inspect IN-OUT_PlcyMAP class type inspect IN-OUT_ClassMAP inspect <------ policy-map type inspect IN-OUT_PlcyMap class type inspect IN-OUT_ClassMAP pass <------ zone security INSIDE zone security OUTSIDE zone-pair security IN->OUT source INSIDE destination OUTSIDE service-policy type inspect IN-OUT_PlcyMAP What is the difference between "inspect", "pass", "drop", "log", and "reset ? I could not found any information on this on Google.

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  • Why does Excel now give me already existing name range error on Copy Sheet?

    - by WilliamKF
    I've been working on a Microsoft Excel 2007 spreadsheet for several days. I'm working from a master template like sheet and copying it to a new sheet repeatedly. Up until today, this was happening with no issues. However, in the middle of today this suddenly changed and I do not know why. Now, whenever I try to copy a worksheet I get about ten dialogs, each one with a different name range object (shown below as 'XXXX') and I click yes for each one: A formula or sheet you want to move or copy contains the name 'XXXX', which already exists on the destination worksheet. Do you want to use this version of the name? To use the name as defined in destination sheet, click Yes. To rename the range referred to in the formula or worksheet, click No, and enter a new name in the Name Conflict dialog box. The name range objects refer to cells in the sheet. For example, E6 is called name range PRE on multiple sheets (and has been all along) and some of the formulas refer to PRE instead of $E$6. One of the 'XXXX' above is this PRE. These name ranges should only be resolved within the sheet within which they appear. This was not an issue before despite the same name range existing on multiple sheets before. I want to keep my name ranges. What could have changed in my spreadsheet to cause this change in behavior? I've gone back to prior sheets created this way and now they give the message too when copied. I tried a different computer and a different user and the same behavior is seen everywhere. I can only conclude something in the spreadsheet has changed. What could this be and how can I get back the old behavior whereby I can copy sheets with name ranges and not get any errors? Looking in the Name Manager I see that the name ranges being complained about show twice, once as scope Template and again as scope Workbook. If I delete the scope Template ones the error goes away on copy however, I get a bunch of #REF errors. If I delete the scope Workbook ones, all seems okay and the errors on copy go away too, so perhaps this is the answer, but I'm nervous about what effect this deletion will have and wonder how the Workbook ones came into existence in the first place. Will it be safe to just delete the Workbook name manager scoped entries and how might these have come into existence without my knowing it to begin with?

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  • Remote access to internal machine (ssh port-forwarding)

    - by MacUsers
    I have a server (serv05) at work with a public ip, hosting two KVM guests - vtest1 & vtest2 - in two different private network - 192.168.122.0 & 192.168.100.0 - respectively, this way: [root@serv05 ~]# ip -o addr show | grep -w inet 1: lo inet 127.0.0.1/8 scope host lo 2: eth0 inet xxx.xxx.xx.197/24 brd xxx.xxx.xx.255 scope global eth0 4: virbr1 inet 192.168.100.1/24 brd 192.168.100.255 scope global virbr1 6: virbr0 inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0 # [root@serv05 ~]# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.100.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr1 xxx.xxx.xx.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 169.254.0.0 0.0.0.0 255.255.0.0 U 1002 0 0 eth0 0.0.0.0 xxx.xxx.xx.62 0.0.0.0 UG 0 0 0 eth0 I've also setup IP FORWARDing and Masquerading this way: iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE iptables --append FORWARD --in-interface virbr0 -j ACCEPT All works up to this point. If I want to remote access vtest1 (or vtest2) first I ssh to serv05 and then from there ssh to vtest1. Is there a way to setup a port forwarding so that vtest1 can be accessed directly from the outside world? This is what I probably need to setup: external_ip (tcp port 4444) -> DNAT -> 192.168.122.50 (tcp port 22) I know it's easily do'able using a SOHO router but can't figure out how can I do that on a Linux box. Any help form you guys?? Cheers!! Update: 1 Now I've made ssh to listen to both of the ports: [root@serv05 ssh]# netstat -tulpn | grep ssh tcp 0 0 xxx.xxx.xx.197:22 0.0.0.0:* LISTEN 5092/sshd tcp 0 0 xxx.xxx.xx.197:4444 0.0.0.0:* LISTEN 5092/sshd and port 4444 is allowed in the iptables rules: [root@serv05 sysconfig]# grep 4444 iptables -A PREROUTING -i eth0 -p tcp -m tcp --dport 4444 -j DNAT --to-destination 192.168.122.50:22 -A INPUT -p tcp -m state --state NEW -m tcp --dport 4444 -j ACCEPT -A FORWARD -i eth0 -p tcp -m tcp --dport 4444 -j ACCEPT But I'm getting connection refused: maci:~ santa$ telnet serv05 4444 Trying xxx.xxx.xx.197... telnet: connect to address xxx.xxx.xx.197: Connection refused telnet: Unable to connect to remote host Any idea what's I'm still missing? Cheers!!

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  • Is there a way to backup AD and DNS in Windows 2008 without backing up the whole Volume?

    - by EtherDragon
    I would like to know if there is a (cost free) way to backup Windows Server 2008 Active Directory and DNS settings without using Windows Server Backup. The problem stems from not having a seperate volume available to store the resulting backup from Windows Server Backup. I examined the command line options with wbadmin and it also expects the destination to be a dedicated volume for the backup. ~ED

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  • Why is Windows 7 not following all routes?

    - by GigabyteProductions
    My computer is connected to my secondary router that's running the 192.168.42.0/24 network and my computer also has a route that directs anything on that network to the router, but for anything on that network other than the router itself, it get's the ICMP response of Reply from 192.168.42.194: Destination host unreachable. (with 192.168.42.194 being my computer). Every other network works, like all of the internet, or addresses on my primary router like 192.168.1.*, just not on the 192.168.42.0/24 network... route print returns: IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 192.168.42.1 192.168.42.194 276 127.0.0.0 255.0.0.0 On-link 127.0.0.1 306 127.0.0.1 255.255.255.255 On-link 127.0.0.1 306 127.255.255.255 255.255.255.255 On-link 127.0.0.1 306 192.168.42.0 255.255.255.0 On-link 192.168.42.194 276 192.168.42.194 255.255.255.255 On-link 192.168.42.194 276 192.168.42.255 255.255.255.255 On-link 192.168.42.194 276 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 192.168.42.194 276 255.255.255.255 255.255.255.255 On-link 127.0.0.1 306 255.255.255.255 255.255.255.255 On-link 192.168.42.194 276 =========================================================================== Persistent Routes: Network Address Netmask Gateway Address Metric 0.0.0.0 0.0.0.0 192.168.42.1 Default =========================================================================== The only time anything is supposed to send an ICMP Host Unreachable response is when there's no route to it, right? So, why is my own computer sending that to ping or tracert when I have the route of 192.168.42.0 with the mask of 255.255.255.0? An IP address of 192.168.42.2 surely fits into that route. If I explicitly add a route for the IP address i am trying to access, it works, like: route add 192.168.42.2 mask 255.255.255.255 192.168.42.1 (the 192.168.42.1 right after mask is gateway, or the device to send the packet to so it can route it further), but why wont it work for the implicit route that's automatically on the table? I disabled my firewall, too (I use Comodo if anyone thinks this still serves as a problem). I'v even tried explicitly adding the gateway of 192.168.42.1 to the 192.168.42.0/24 route instead of it routing through 0.0.0.0's gateway, which is what On-link does. but that didn't work either, so it's not a gateway specification problem. If the host was really unreachable, it would be the router's IP address (192.168.42.1) sending that to me... This network is all of my creation, so there's no problem such as an administrator locking me out, because i am the administrator.

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  • Is it possible to copy a set of files, but automatically skip if file already exists?

    - by awe
    I know that the copy command has an option to automatically replace a file if it already exists, but I want to know if it is a way to copy the files only if they not already exist (/Y). I do not know the actual file names in the batch code, as I copy from the source using wildcards in the copy command: copy *.zip c:\destination The reason I want this instead of automatic overwrite is that the files are large, and to skip existing would save a lot of execution time.

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  • How Spanning Tree Protocol detects Loops

    - by AMIT
    For last few days I've been reading about Spanning Tree Protocol ,L2 protocol and understood how it prevents loop in network ,various steps in STP but one thing i wanted to know how STP actually detects the loops in network so that it can prevent it.Somewhere I read STP uses BPDU as probe and detects loops I mean how it happen is when switch send a BPDU with Destination Address as multicast and receive same BPDU again mean there is loop in network . But is it how STP detects loops in network?

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  • Is there a way to backup AP and DNS in Windows 2008 without backing up the whole Volume?

    - by EtherDragon
    I would like to know if there is a (cost free) way to backup Windows Server 2008 Active Directory and DNS settings without using Windows Server Backup. The problem stems from not having a seperate volume available to store the resulting backup from Windows Server Backup. I examined the command line options with wbadmin and it also expects the destination to be a dedicated volume for the backup. ~ED

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  • Chrome: Save as dialogue creates temp file in download directory, I want to change this location

    - by Gabardine
    I've set the download directory for Chrome to be my desktop, but that means that whenever I want to "Save As" it creates a temp file on my desktop until I select the final download destination and close the dialogue. This is deeply frustrating since I browse windowed and I keep seeing the damn things pop up and disappear in the corner of my eye, is there any way to change the directory in which temp files are created in this manner?

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  • Configure Postfix with Virtual Mailboxes to forward to a script

    - by keykiller91
    I am using the Postfix MTA with a virtual configuration from MySQL for the Users and Forwardings. Now I want some Adresses (that are dynamicaly generated, for writing via E-Mail to a Forum) to be forwarded to a php-script. I already have tried to put the script quoted and piped as destination bit it doesn't work. "|php -q /path/to/script.php" But if I send a mail to that domain it says: User “|php -q /path/to/script.php"@mydomain.tld not found

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  • Asterisk server firewall script allows 2-way audio from incoming calls, but not on outgoing?

    - by cappie
    I'm running an Asterisk PBX on a virtual machine directly connected to the Internet and I really want to prevent script kiddies, l33t h4x0rz and actual hackers access to my server. The basic way I protect my calling-bill now is by using 32 character passwords, but I would much rather have a way to protect The firewall script I'm currently using is stated below, however, without the established connection firewall rule (mentioned rule #1), I cannot receive incoming audio from the target during outgoing calls: #!/bin/bash # first, clean up! iptables -F iptables -X iptables -t nat -F iptables -t nat -X iptables -t mangle -F iptables -t mangle -X iptables -P INPUT ACCEPT iptables -P FORWARD DROP # we're not a router iptables -P OUTPUT ACCEPT # don't allow invalid connections iptables -A INPUT -m state --state INVALID -j DROP # always allow connections that are already set up (MENTIONED RULE #1) iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT # always accept ICMP iptables -A INPUT -p icmp -j ACCEPT # always accept traffic on these ports #iptables -A INPUT -p tcp --dport 80 -j ACCEPT iptables -A INPUT -p tcp --dport 22 -j ACCEPT # always allow DNS traffic iptables -A INPUT -p udp --sport 53 -j ACCEPT iptables -A OUTPUT -p udp --dport 53 -j ACCEPT # allow return traffic to the PBX iptables -A INPUT -p udp -m udp --dport 50000:65536 -j ACCEPT iptables -A INPUT -p udp -m udp --dport 10000:20000 -j ACCEPT iptables -A INPUT -p udp --destination-port 5060:5061 -j ACCEPT iptables -A INPUT -p tcp --destination-port 5060:5061 -j ACCEPT iptables -A INPUT -m multiport -p udp --dports 10000:20000 iptables -A INPUT -m multiport -p tcp --dports 10000:20000 # IP addresses of the office iptables -A INPUT -s 95.XXX.XXX.XXX/32 -j ACCEPT # accept everything from the trunk IP's iptables -A INPUT -s 195.XXX.XXX.XXX/32 -j ACCEPT iptables -A INPUT -s 195.XXX.XXX.XXX/32 -j ACCEPT # accept everything on localhost iptables -A INPUT -i lo -j ACCEPT # accept all outgoing traffic iptables -A OUTPUT -j ACCEPT # DROP everything else #iptables -A INPUT -j DROP I would like to know what firewall rule I'm missing for this all to work.. There is so little documentation on which ports (incoming and outgoing) asterisk actually needs.. (return ports included). Are there any firewall/iptables specialists here that see major problems with this firewall script? It's so frustrating not being able to find a simple firewall solution that enabled me to have a PBX running somewhere on the Internet which is firewalled in such a way that it can ONLY allows connections from and to the office, the DNS servers and the trunk(s) (and only support SSH (port 22) and ICMP traffic for the outside world). Hopefully, using this question, we can solve this problem once and for all.

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  • SQL SERVER – Signal Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28

    - by pinaldave
    In this post, let’s delve a bit more in depth regarding wait stats. The very first question: when do the wait stats occur? Here is the simple answer. When SQL Server is executing any task, and if for any reason it has to wait for resources to execute the task, this wait is recorded by SQL Server with the reason for the delay. Later on we can analyze these wait stats to understand the reason the task was delayed and maybe we can eliminate the wait for SQL Server. It is not always possible to remove the wait type 100%, but there are few suggestions that can help. Before we continue learning about wait types and wait stats, we need to understand three important milestones of the query life-cycle. Running - a query which is being executed on a CPU is called a running query. This query is responsible for CPU time. Runnable – a query which is ready to execute and waiting for its turn to run is called a runnable query. This query is responsible for Signal Wait time. (In other words, the query is ready to run but CPU is servicing another query). Suspended – a query which is waiting due to any reason (to know the reason, we are learning wait stats) to be converted to runnable is suspended query. This query is responsible for wait time. (In other words, this is the time we are trying to reduce). In simple words, query execution time is a summation of the query Executing CPU Time (Running) + Query Wait Time (Suspended) + Query Signal Wait Time (Runnable). Again, it may be possible a query goes to all these stats multiple times. Let us try to understand the whole thing with a simple analogy of a taxi and a passenger. Two friends, Tom and Danny, go to the mall together. When they leave the mall, they decide to take a taxi. Tom and Danny both stand in the line waiting for their turn to get into the taxi. This is the Signal Wait Time as they are ready to get into the taxi but the taxis are currently serving other customer and they have to wait for their turn. In other word they are in a runnable state. Now when it is their turn to get into the taxi, the taxi driver informs them he does not take credit cards and only cash is accepted. Neither Tom nor Danny have enough cash, they both cannot get into the vehicle. Tom waits outside in the queue and Danny goes to ATM to fetch the cash. During this time the taxi cannot wait, they have to let other passengers get into the taxi. As Tom and Danny both are outside in the queue, this is the Query Wait Time and they are in the suspended state. They cannot do anything till they get the cash. Once Danny gets the cash, they are both standing in the line again, creating one more Signal Wait Time. This time when their turn comes they can pay the taxi driver in cash and reach their destination. The time taken for the taxi to get from the mall to the destination is running time (CPU time) and the taxi is running. I hope this analogy is bit clear with the wait stats. You can check the Signalwait stats using following query of Glenn Berry. -- Signal Waits for instance SELECT CAST(100.0 * SUM(signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%signal (cpu) waits], CAST(100.0 * SUM(wait_time_ms - signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%resource waits] FROM sys.dm_os_wait_stats OPTION (RECOMPILE); Higher the Signal wait stats are not good for the system. Very high value indicates CPU pressure. In my experience, when systems are running smooth and without any glitch the Signal wait stat is lower than 20%. Again, this number can be debated (and it is from my experience and is not documented anywhere). In other words, lower is better and higher is not good for the system. In future articles we will discuss in detail the various wait types and wait stats and their resolution. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • SQL SERVER – Single Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28

    - by pinaldave
    In this post, let’s delve a bit more in depth regarding wait stats. The very first question: when do the wait stats occur? Here is the simple answer. When SQL Server is executing any task, and if for any reason it has to wait for resources to execute the task, this wait is recorded by SQL Server with the reason for the delay. Later on we can analyze these wait stats to understand the reason the task was delayed and maybe we can eliminate the wait for SQL Server. It is not always possible to remove the wait type 100%, but there are few suggestions that can help. Before we continue learning about wait types and wait stats, we need to understand three important milestones of the query life-cycle. Running - a query which is being executed on a CPU is called a running query. This query is responsible for CPU time. Runnable – a query which is ready to execute and waiting for its turn to run is called a runnable query. This query is responsible for Single Wait time. (In other words, the query is ready to run but CPU is servicing another query). Suspended – a query which is waiting due to any reason (to know the reason, we are learning wait stats) to be converted to runnable is suspended query. This query is responsible for wait time. (In other words, this is the time we are trying to reduce). In simple words, query execution time is a summation of the query Executing CPU Time (Running) + Query Wait Time (Suspended) + Query Single Wait Time (Runnable). Again, it may be possible a query goes to all these stats multiple times. Let us try to understand the whole thing with a simple analogy of a taxi and a passenger. Two friends, Tom and Danny, go to the mall together. When they leave the mall, they decide to take a taxi. Tom and Danny both stand in the line waiting for their turn to get into the taxi. This is the Signal Wait Time as they are ready to get into the taxi but the taxis are currently serving other customer and they have to wait for their turn. In other word they are in a runnable state. Now when it is their turn to get into the taxi, the taxi driver informs them he does not take credit cards and only cash is accepted. Neither Tom nor Danny have enough cash, they both cannot get into the vehicle. Tom waits outside in the queue and Danny goes to ATM to fetch the cash. During this time the taxi cannot wait, they have to let other passengers get into the taxi. As Tom and Danny both are outside in the queue, this is the Query Wait Time and they are in the suspended state. They cannot do anything till they get the cash. Once Danny gets the cash, they are both standing in the line again, creating one more Single Wait Time. This time when their turn comes they can pay the taxi driver in cash and reach their destination. The time taken for the taxi to get from the mall to the destination is running time (CPU time) and the taxi is running. I hope this analogy is bit clear with the wait stats. You can check the single wait stats using following query of Glenn Berry. -- Signal Waits for instance SELECT CAST(100.0 * SUM(signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%signal (cpu) waits], CAST(100.0 * SUM(wait_time_ms - signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%resource waits] FROM sys.dm_os_wait_stats OPTION (RECOMPILE); Higher the single wait stats are not good for the system. Very high value indicates CPU pressure. In my experience, when systems are running smooth and without any glitch the single wait stat is lower than 20%. Again, this number can be debated (and it is from my experience and is not documented anywhere). In other words, lower is better and higher is not good for the system. In future articles we will discuss in detail the various wait types and wait stats and their resolution. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • Hello it’s your server calling

    - by GrumpyOldDBA
    This is nothing exciting but I've always found this startup procedure  very useful. All this simple procedure does is send you an email if the SQL Service Starts. If your Server is a cluster it will tell you which node you're on. -- On it's own this procedure can't actually be used as I route the output through another procedure, dbasp_SendMessage, this procedure routes a passed message to either a smtp email or a log table or both, the destination is set in a server config table...(read more)

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  • Ubuntu tweak not showing all the menus

    - by Gaurav Butola
    Ubuntu-Tweak doesn't have the option Startup which includes Session Manager Session Control and few other options are not there. I am running the latest version available to download. I remember having all those menus in lucid. for a better difference comparison see the menus in the ubuntu tweak homepage http://ubuntu-tweak.com/ with mine.... how can I get these option back. here is the error I get when I run Ubuntu Tweak from terminal ERROR:dbus.proxies:Introspect error on :1.142:/com/ubuntu_tweak/daemon: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.AccessDenied: Rejected send message, 1 matched rules; type="method_call", sender=":1.141" (uid=1000 pid=16550 comm="/usr/bin/python) interface="org.freedesktop.DBus.Introspectable" member="Introspect" error name="(unset)" requested_reply=0 destination=":1.142" (uid=0 pid=16560 comm="/usr/bin/python)) Update: I installed the same deb on another computer and that has nothing wrong. all the menus are listed fine.

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