… it is a lot larger problems with MySQL 5.5 with addition of user variables, stored procedures, prepared statements etc which can… at how it uses MySQL to identify potential causes. Is it working with large blobs ? Using user variables ? Prepared Statements ? memory tables… of resources prepared statements take on server. There is no comparable variables of how many user variables are allocated (and how much memory…
Post: Introducing the pmp-check-mysql-status Nagios Plugin
March 29, 2012 By Leave a Comment
… of status counters and variables. This is the pmp-check-mysql-status plugin, which can perform computations on status variables. By default, I recommend using it only for two purposes: Check whether the Uptime variable is too small, indicating the server…
Post: InnoDB's gap locks
March 27, 2012 By 15 Comments
…. This makes reads consistent and therefore makes the replication between servers consistent. If you execute SELECT * FROM id > 1000 FOR UPDATE… that the second one is a global variable that affects all sessions and needs a server restart to change its value. Both…/doc/refman/5.1/en/innodb-locks-set.html. Conclusion MySQL uses REPEATABLE READ as the default isolation level so it…
Comment: PHP Sessions - Files vs Database Based
April 10, 2012 By 38 Comments
… mysql backed memcached as session handler, there still exists problem with concurrency between simultaneous requests overwriting each others $_SESSION variable. … entity. It’s good for reliably locked simple single server installation, but not for distributed environments. I would recommending …
Post: MySQL Server Variables - SQL layer or Storage Engine specific.
June 8, 2006 By 14 Comments
MySQL Server has tons of variables which may be adjusted to change behavior or for performance … and HEAP for in memory tables. So first MySQL versions did not bother naming variables with storage engines prefix. This is why… it mean MyISAM variables are not important ? Not really. You still have some tables in MyISAM format in “mysql” database. Plus HEAP…
Post: Can we improve MySQL variable handling ?
February 18, 2012 By 8 Comments
MySQL Settings (also known as Server Variables) have interesting property. When you set variable in running server this change is not persisted in any way… easily because MySQL Server does not seems to have an easy way to check what was the default value for given Server Variable. The…
Post: Helgrinding MySQL with InnoDB for Synchronisation Errors, Fun and Profit
November 24, 2011 By 2 Comments
… widely used for the MySQL server development: there is support for it in the MySQL Test Framework, DBQP, and the server source is properly… are LOCK_global_system_variables and LOCK_system_variables_hash. Deadlock is possible when one connection issues SHOW VARIABLES or equivalent while another…
Post: What to tune in MySQL Server after installation
September 29, 2006 By 116 Comments
… as MySQL DBAs or be involved with MySQL Performance in some way is to ask them what should be tuned in MySQL Server straight… servers are where in wild which are running with default settings. Even though you can tune quite a lot of variables in MySQL Servers… less secure as you can lose transactions even in case MySQL Server crashes. Value 2 only cause data loss with full OS…
Post: How to Monitor MySQL with Percona's Nagios Plugins
February 22, 2012 By 8 Comments
… disk. The database server will continue to function, however, because the file isn’t really deleted. The MySQL server keeps an open filehandle to the file, and it won’t be deleted until the server restarts, so… use the pmp-check-mysql-status plugin to alert when the server‘s Uptime variable is too small. The server is approaching max_connections…
Post: How Percona diagnoses MySQL server stalls
March 3, 2011 By 6 Comments
… thing to check for. VARIABLE=${VARIABLE:-Threads_connected} You need to change the threshold to 15, and the variable to Threads_running. Check… script can log into MySQL (if necessary, put a password into .my.cnf, or in the MYSQLOPTIONS variable). Now you can simply…, and sometimes the disks are responding very well but the server is abusing them and overloading them. And sometimes, of course…
