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• Make a snapshot of a live mySQL database with myISAM & innoDB tables without locking

  - by Artem

  We have a live database in production where we are running out of space on the server. So I would like to transfer to a new server without any downtime (or as little downtime as possible). In general, I would also like to have a hot failover copy of the database available. I would like to use replication to get all of the data copied to the new machine, and then at some point flip a switch and have that new machine become the master (normal failover scenario). My problem is that I am not sure how to initialize replication without locking the db to make the initial snapshot I will use? Is there any way to do this? I know I could do it using single-transaction if I was using innoDB, but very unfortunately we have some myISAM tables in there (in fact the largest 150GB table is myISAM and I want to switch it to InnoDB but I can't do it until I have more space & a hot copy to switch to). Any ideas? Is there some way to make such a snapshot? Or is there alternatively a way to get replication to "catch up" without an snapshot for initialization?

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• SQL Server Read Locking behavior

  - by Charles Bretana

  When SQL Server Books online says that "Shared (S) locks on a resource are released as soon as the read operation completes, unless the transaction isolation level is set to repeatable read or higher, or a locking hint is used to retain the shared (S) locks for the duration of the transaction." Assuming we're talking about a row-level lock, with no explicit transaction, at default isolation level (Read Committed), what does "read operation" refer to? The reading of a single row of data? The reading of a single 8k IO Page ? or until the the complete Select statement in which the lock was created has finished executing, no matter how many other rows are involved? NOTE: The reason I need to know this is we have a several second read-only select statement generated by a data layer web service, which creates page-level shared read locks, generating a deadlock due to conflicting with row-level exclusive update locks from a replication prcoess that keeps the server updated. The select statement is fairly large, with many sub-selects, and one DBA is proposing that we rewrite it to break it up into multiple smaller statements (shorter running pieces), "to cut down on how long the locks are held". As this assumes that the shared read locks are held till the complete select statement has finished, if that is wrong (if locks are released when the row, or the page is read) then that approach would have no effect whatsoever....

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• NFS-shared file-system is locking up

  - by fredden

  Our NFS-shared file-system is locking up. Please feel free to ask any questions you feel relevant. :) At the time, there are a lot of processes in "disk sleep" state, and the load averages on our machines sky-rocket. The machines are responsive on SSH, but our the majority of our websites (apache+mod_php) just hang, as does our email system (exim+dovecot). Any websites which don't require write access to the file-system continue to operate. The load averages continue to rise until some kind of time-out is reached, but for at least 10-15 minutes. I've seen load averages over 800, yet the machines are still responsive for actions which don't require writing to the shared file-system. I've been investigating a variety of options, which have all turned out to be red-herrings: nagios, proftpd, bind, cron tasks. I'm seeing these messages in the file server's system log: Jul 30 09:37:17 fs0 kernel: [1810036.560046] statd: server localhost not responding, timed out Jul 30 09:37:17 fs0 kernel: [1810036.560053] nsm_mon_unmon: rpc failed, status=-5 Jul 30 09:37:17 fs0 kernel: [1810036.560064] lockd: cannot monitor node2 Jul 30 09:38:22 fs0 kernel: [1810101.384027] statd: server localhost not responding, timed out Jul 30 09:38:22 fs0 kernel: [1810101.384033] nsm_mon_unmon: rpc failed, status=-5 Jul 30 09:38:22 fs0 kernel: [1810101.384044] lockd: cannot monitor node0 Software involved: VMWare, Debian lenny (64bit), ancient Red Hat (32 bit) (version 7 I believe), Debian etch (32bit) NFS, apache2+mod_php, exim, dovecot, bind, amanda, proftpd, nagios, cacti, drbd, heartbeat, keepalived, LVS, cron, ssmtp, NIS, svn, puppet, memcache, mysql, postgres Joomla!, Magento, Typo3, Midgard, Symfony, custom php apps

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• Disadvantages of MySQL Row Locking

  - by Nyxynyx

  I am using row locking (transactions) in MySQL for creating a job queue. Engine used is InnoDB. SQL Query START TRANSACTION; SELECT * FROM mytable WHERE status IS NULL ORDER BY timestamp DESC LIMIT 1 FOR UPDATE; UPDATE mytable SET status = 1; COMMIT; According to this webpage, The problem with SELECT FOR UPDATE is that it usually creates a single synchronization point for all of the worker processes, and you see a lot of processes waiting for the locks to be released with COMMIT. Question: Does this mean that when the first query is executed, which takes some time to finish the transaction before, when the second similar query occurs before the first transaction is committed, it will have to wait for it to finish before the query is executed? If this is true, then I do not understand why the row locking of a single row (which I assume) will affect the next transaction query that would not require reading that locked row? Additionally, can this problem be solved (and still achieve the effect row locking does for a job queue) by doing a UPDATE instead of the transaction? UPDATE mytable SET status = 1 WHERE status IS NULL ORDER BY timestamp DESC LIMIT 1

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• Why use SyncLocks in .NET for simple operations when Interlocked class is available?

  - by rwmnau

  I've been doing simple multi-threading in VB.NET for a while, and have just gotten into my first large multi-threaded project. I've always done everything using the Synclock statement because I didn't think there was a better way. I just learned about the Interlocked Class - it makes it look as though all this: Private SomeInt as Integer Private SomeInt_LockObject as New Object Public Sub IntrementSomeInt Synclock SomeInt_LockObject SomeInt += 1 End Synclock End Sub Can be replaced with a single statement: Interlocked.Increment(SomeInt) This handles all the locking internally and modifies the number. This would be much simpler than writing my own locks for simple operations (longer-running or more complicated operations obviously still need their own locking). Is there a reason why I'd rolling my own locking, using dedicated locking objects, when I can accomplish the same thing using the Interlocked methods?

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• DataReader Behaviour With SQL Server Locking

  - by Graham

  We are having some issues with our data layer when large datasets are returned from a SQL server query via a DataReader. As we use the DataReader to populate business objects and serialize them back to the client, the fetch can take several minutes (we are showing progress to the user :-)), but we've found that there's some pretty hard-core locking going on on the affected tables which is causing other updates to be blocked. So I guess my slightly naive question is, at what point are the locks which are taken out as a result of executing the query actually relinquished? We seem to be finding that the locks are remaining until the last row of the DataReader has been processed and the DataReader is actually closed - does that seem correct? A quick 101 on how the DataReader works behind the scenes would be great as I've struggled to find any decent information on it. I should say that I realise the locking issues are the main concern but I'm just concerned with the behaviour of the DataReader here.

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• Record locking problem between linux and Windows

  - by PabloG

  I need to run a bunch of old DOS FoxPro / Clipper applications in linux under DOSEMU. The programs access their "databases" located on a network server (could be a Windows or Linux server) Actually, the programs ran fine, but I cannot manage to make the record locking work as supposed: I can run a program in two terminals (or the server and any terminal for instance) and lock the same record in both. Now, I'm using Tiny Core Linux as terminal and Windows XP as server, accesing the shared files via CIFS and the latest DOSEMU (1.4.0), but I tried with various combinations of server (Ubuntu 7 to 9, Damn Small Linux, XP) <- protocol (CIFS, samba, various versions of smbclient) <- client (same as server) with no luck I tried to configure the server part to work without oplocks in samba (after reading the entire O'Reilly Samba book locking chapter in http://oreilly.com/catalog/samba/chapter/book/ch05_05.html ) and in XP (\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\UseOpportunisticLocking = 0) but the problem persist. Any ideas? TIA, Pablo

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• Do MySQL Locked Tables affect related Views?

  - by CogitoErgoSum

  So after reading http://stackoverflow.com/questions/1415602/performance-in-pdo-php-mysql-transaction-versus-direct-execution in regards to performance issues I was thinking about I did some research on locking tables in MySQL. On http://dev.mysql.com/doc/refman/5.0/en/table-locking.html Table locking enables many sessions to read from a table at the same time, but if a session wants to write to a table, it must first get exclusive access. During the update, all other sessions that want to access this particular table must wait until the update is done. This part struck me particularly becuase most of our queries will be updates rather than inserts. I was wondering if one created a table called foo on which all updates/inserts were carried out and then a view called foo_view (A copy of foo, or perhaps foo and a linkage of several other tables plus foo) on which all selects occured, would this locking issue still occur? That is, would SELECT quries on foo_view still have to wait for an update to finish on foo?

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• What is the best WebDAV client for Windows?

  - by dr0ne

  The support of locking will be preferred.

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• What privilege level is required on a Windows client workstation on an ActiveDomain to break file lo

  - by Mike Burton

  I'm not sure if I should be asking this here or on StackOverflow, but here goes: I'm part of a team maintaining a document management application, and I'm trying to figure out Windows file locking permissions. We use a utility somebody downloaded years ago called psunlock to remotely close all locks on a file. We recently discovered that this does not work across different domains on our VPN. A little bit of digging lead me to the samba manual's discussion of file locking. I still don't really "get it", though. Does anyone have any insight to share into how the process of locking and breaking locks on files works in a network context? My thinking is that privileges are required both on the file appliance and on the client workstations which hold locks. Is that accurate? Can anyone give a more specific version? Ideally I'm looking for something along the lines of A user must have privilege level X in order to break locks held from a client workstation. In practice I'd be happy with a hotlink to a good white paper on the subject.

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• Follow-up Answers for my Australia Classes

  - by Kalen Delaney

  I was out of the country for the last two weeks of March, delivering classes in Brisbane and Sydney, which were organized by WardyIT . It was a great visit and there were 24 terrific students! As is sometimes (perhaps often?) the case, there were questions posed that I couldn’t answer during class, so here are a couple of follow-up answers. 1. I brought up the fact that SQLS 2012 generates a warning message when there are ‘too many’ Virtual Log Files (VLFs) in a database. (It turns out the message...(read more)

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• Apache reaching MaxClients and locking the server

  - by Rodrigo Sieiro

  Hi. I currently have an Apache2 server running with mpm-prefork and mod_php on a OpenVZ VPS with 512M real / 1024M burstable RAM (no swap). After running some tests, I found that the maximum process size Apache gets is 23M, so I've set MaxClients to 25 (23M x 25 = 575 MB, ok for me). I decided to run some load tests on my server, and the results left me puzzled. I'm using ab on my desktop machine requesting the main page from a wordpress blog. When I run ab with 24 concurrent connections, everything seems fine. Sure, CPU goes up, free RAM goes down, and the result is about 2-3s response time per request. But if I run ab with 25 concurrent connections (my server limit), Apache just hangs after a couple of seconds. It starts processing the requests, then it stops responding, CPU goes back to 100% idle and ab times out. Apache log says it reached MaxClients. When this happens, Apache keeps itself locked up with 25 running processes (they're all in "W" if I check server status) and only after the TimeOut setting the processes start to die and the server starts responding again (in my case it's set to 45). My question: is that expected behaviour? Why Apache just dies when it reaches MaxClients? If it works with 24 connections, shouldn't it work with 25, just taking maybe more time to respond each request and queueing up the rest? It sounds kinda strange to me that any kid running ab can alone kill a webserver just by setting the concurrent connections to the servers MaxClients.

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• Apache MaxClients reaching max and locking the server

  - by Rodrigo Sieiro

  Hi. I currently have an Apache2 server running with mpm-prefork and mod_php on a OpenVZ VPS with 512M real / 1024M burstable RAM (no swap). After running some tests, I found that the maximum process size Apache gets is 23M, so I've set MaxClients to 25 (23M x 25 = 575 MB, ok for me). I decided to run some load tests on my server, and the results left me puzzled. I'm using ab on my desktop machine requesting the main page from a wordpress blog. When I run ab with 24 concurrent connections, everything seems fine. Sure, CPU goes up, free RAM goes down, and the result is about 2-3s response time per request. But if I run ab with 25 concurrent connections (my server limit), Apache just hangs after a couple of seconds. It starts processing the requests, then it stops responding, CPU goes back to 100% idle and ab times out. Apache log says it reached MaxClients. When this happens, Apache keeps itself locked up with 25 running processes (they're all in "W" if I check server status) and only after the TimeOut setting the processes start to die and the server starts responding again (in my case it's set to 45). My question: is that expected behaviour? Why Apache just dies when it reaches MaxClients? If it works with 24 connections, shouldn't it work with 25, just taking maybe more time to respond each request and queueing up the rest? It sounds kinda strange to me that any kid running ab can alone kill a webserver just by setting the concurrent connections to the servers MaxClients.

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• IPFW not locking people out

  - by Cole

  I've had some brute-forcing of my ssh connection recently, so I got fail2ban to hopefully prevent that. I set it up, and started testing it out by giving wrong passwords on my computer. (I have physical access to the server if I need to unblock myself) However, it never stops me from entering passwords. I see in /var/log/fail2ban.log that fail2ban kicked in and banned me, and there's a ipfw entry for my IP, but I'm not locked out. I've changed the configuration around, and then tried just using the ipfw command myself, but nothing seems to lock me out. I've tried the following blocks: 65300 deny tcp from 10.0.1.30 to any in 65400 deny ip from 10.0.1.30 to any 65500 deny tcp from 10.0.1.30 to any My firewall setup has a "allow ip from any to any" rule after these though, maybe that's the problem? I'm using Mac OS 10.6 (stock ipfw, it doesn't seem to have a --version flag) Thanks in advance.

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• ESXi 4.0 Guests Locking up

  - by Brendan Sherwin

  I installed ESXi 4.0 on an HP Proliant g5 with a 64bit Xeon processor and took advantage of the free license as I work for a public school. I created two instances of server 2003 from scratch, one to be the DC, DHCP, the other to be a file server and DNS/DHCP backup. I had both guests up and running fine, setup my user accounts, transferred the data, etc etc. Once I joined a client machine to the domain, I would find that both of my Windows guests would lock up. Sometimes it would be for five or so minutes, once it was overnight. The "locked up" state means that as far I could tell, all services were stopped; dhcp no longer handed out IP's, DNS stopped working, I couldn't RDP into the server. The ESXi host, my HP server, was still running fine. VSphere was working, and I could look at the performance of the individual guests.I would try Powering off the hosts from inside VSPhere, and the hosts would start powering off, but get stuck at 95%, and stay that way, sometimes only for 10 minutes, others for hours. Several times I had to restart ESXi from it's console in order to restart my machines. Now, can anyone tell me what is happening, and how I can fix it, or take steps to prevent it? I hired a consultant to come take a look at it, someone who's experience and knowledge I trust, and he told me he had never seen anything like this ever before. He spoke to a friend of his who is VM certified, and he also said he had never heard of this issue. Thanks for your replies, and I'll do my best to respond ASAP. Currently, the server is powered off, and I've reinstituted my nine year old Server 2000 boxes, and I'm considering installing ESXi 3.5. Does anyone know a host created in 4.0 will work in 3.5? I'd really like to avoid having to rebuild those accounts! I know 4.0 works on this server, as I have another server in another school with the same exact hardware running 4.0 fine. Brendan

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• Locking sharepoint list item

  - by user39157

  I have a sharepoint custom list which has 5 columns ..the user should fill in first three columns and the other two should be locked..when the user enters the items and start the workflow if the workflow gets approved the 3 columns should be locked for editing and then the other two should be available for editing . Can someone please tell me how can i achieve this. Thanks

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• Postgres 9.0 locking up, 100% CPU

  - by Jake

  We are having a problem where our Postgres 9.0 server occasionally locks up and kills our webapp. Restarting Postgres fixes the problem. Here's what I've been able to observe: First, usage of one CPU jumps to 100% for a few minutes Disk operations drop to ~0 during this time Database operations drop to 0 (blocks and tuples per sec) Logs show during this time: WARNING: worker took too long to start; cancelled WARNING: worker took too long to start; cancelled No Queries in logs (only those over 200ms are logged) No unusually long-running queries logged before or during Then the second CPU jumps to 100% The number of postgres processes jumps from the usual 8-10 to ~20 Matched by a spike in Postgres Blocks per second (about twice normal) Logs show LOG: could not accept SSL connection: EOF detected Queries are running but slow Restarting postgres returns everything to normal Setup: Server: Amazon EC2 Large Ubuntu 10.04.2 LTS Postgres 9.0.3 Dedicated DB server Does anyone have any idea what's causing this? Or any suggestions about what else I should be checking out?

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• Stop Cisco AnyConnect from locking down the NIC

  - by Johannes Rössel

  Cisco's VPN crapclients (including the AnyConnect one) have the nasty habit of clobbering all NICs on the system you're using them. The old client had a checkbox in the connection options that allowed you to use other network interfaces while being connected while the AnyConnect client doesn't have any options at all, seemingly. But they both lock down the network interface they are using to connect to the VPN. Since I am forced to use AnyConnect to actually have an internet connection and I like to control a second computer at home via RDP (over the same network interface so far) this doesn't quite work out. With the old client IPv6 still worked just fine, though AnyConnect seems to dislike that as well now. Is there any way to still use the same network interface for LAN access? I actually don't really care about any possible security implications (which might be why Cisco does this) as it's my freaking internet connection and not a secure way of working from home. The trade-off is quite different :-)

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• Windows DFS - file locking & replication?

  - by Adam Salkin

  I'm in a small company that has offices on the east and west coasts of America and also various people working from their homes. There are Windows Servers already in the offices. I think that Microsoft Windows DFS will do what I want, but despite reading the web site, I'm really not sure, so I'm hoping that someone can confirm if it will do all the following: (For various personnel / political reasons I know that a proposal for a Microsoft Windows system has more chance of being accepted than any *nix system) Creation of a Folder so that any files in this folder will automatically be available on the servers in all the offices. When anyone opens up one of these shared files on any of servers, the copies on all the servers will automatically be locked. And when they close the file, the updates automatically get copied to the file on all the servers. VPN access to these folders for people working outside the offices. Bandwidth at the main offices varies from 6 Mb/s to 20Mb/s. Files are Excel / Word / AutoCAD ranging in size from 100KB to 4MB. Thank you.

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• Locking down a box on the web

  - by glowcoder

  I'm a Java developer who is looking to put a game on the web. I'm not much of a web or server guy, though, and frankly I seem a little lost at where I should start with putting something on the web. My application works fine on my machine, and I'm sure I can make it work fine on any box I put it on. But the security of that box is pretty important. If I sign up for a standard hosting package (let's say from GoDaddy or something) can I simply tell them "make port 12345 open for communication" and let them handle the rest of the security details? If I can't, what are the things I'm going to need to know to prevent my game server from getting hacked to shreds? (Links to solid resources fine by me!) Thanks!

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• Locking User account created under Windows Authentication in SQL Server

  - by Santhosha Kaldambe

  Hi, As per my project requirement i need to lock a user in SQL Server(Which is created using Windows Authentication). Is there any way to do this? Thanks for the help Santhosh

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• Tying down a cloud by virtualizing everything and then locking VMs to real hardware as necessary

  - by tudor

  I'm looking for a cloud software solution that: Can run on both server and desktop machines; Virtualizes hardware and has the option of exposing each real machine to the cloud; Allows a VM to be "locked" to a set of real hardware capabilities and stay there until moved (e.g. a user's "real" desktop); Allows a VM to link to some types of devices elsewhere (e.g. USB/serial via ethernet); and Is geography-aware to control movement of VMs between real networks. I'm aware that this may be the holy grail of virtualization, and I've searched alot. Some solutions appear to meet some criteria but not others. Most cloud implementations appear to ignore real hardware, for example. I realise that this may be solved by using three different implementations in combination: A standard cloud server farm. A bare-metal network backup utility with PXEBoot. VNC and/or VDI. (VNC obviously would require the real hardware to be running.) This combination, however, has some serious drawbacks that I'd like to solve by treating it as one system. My explanation follows... I have a network of real servers and desktops in multiple locations. I've virtualized servers before using Virtualbox and that's worked quite well. I've even connected USB devices to VMs on servers. I would like to virtualize the desktops in all my offices to facilitate movement of desktops, remote access (e.g. VDI) and bare-metal backups. However, I know that there are problems with this. For example, some desktops have specific hardware (e.g. 3D graphics cards, USB devices, etc) that limit their mobility. Geographic constraints also limit movement in that VMs can be moved easily within offices, but transferring between offices is not always preferable. What I would like to find is a system that can virtualize everything from bare-metal easily by maintaining an abstraction layer on each client and server machine that exposes the hardware available and runs as a cloud. Then certain VMs would be "locked" to specific hardware (so that, e.g. the VM runs only on their own desktop.) This would be required for situations where speed is important (e.g. 3D graphics pass-through). In addition, abstracted low-speed devices (e.g. USB) could be piped from real hardware to a VM in the cloud. This is important since if a VM is taken down, another VM can connect to the real hardware for minimum downtime.

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• Problem IIS 7.0 Locking files durring upload

  - by viscious

  I am running a server 2008 with iis7 and the ftp addon on to iis 7.0 I have the ftp site configured and mostly working Except that about 70% of the time when transferring a file the upload will hang forever. If I disconnect the ftp client and reconnect and try to upload the same file I will get an error on the client saying the file is locked. I have to restart the ftp service to clear the lock. I fired up process explorer and did a search on the file in question and sure enough the ftp service has a lock on the file and it takes around 20 minutes to release the lock on its own (and sometimes longer). This lock stays around even after I disconnect the client. Like I said this only happens about 70% of the time, the other 30% of the time it goes through just fine. Things i have verified. -Not a firewall issue. Server is using passive port range 8000-9000 which is allowed on the firewall. -Not a nat issue, server has a globally rout-able ip address -all recommended/required updates installed I have 5 other servers in a very similar configuration and this is the only one i have problems with.

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• Remote Desktop Locking issue

  - by Mohammed

  Whenever I take the RDP to my laptop & when i disconnects the remote session it doesn't get locked. Please let me know the answer Mohammed Hussain

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• Multi Monitor setup goes crazy after locking/unlocking Vista machine

  - by Farseeker

  Give me a 10-blade quad-processor quad-core Opteron centre and ask me to configure failover/load balancing and I'd be happy to, but the following problem has got me completely stumped. My Vista Business Professional machine, running Ultramon, has three monitors attached. When I lock the machine (to go to the delicious cafe around the corner), the monitor layout stays correct. When I unlock it, I watch as all my screens flicker (as they are being re-configured), and Vista chooses some crazy layout for the monitors. The most recent one is below, but it's never consistant. Any ideas what might cause this? It's Vista Business, with UltraMon 3.0 (exiting Ultramon makes no difference).

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