…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 14 Comments
…. This makes reads consistent and therefore makes the replication between servers consistent. If you execute SELECT * FROM id > 1000 FOR UPDATE… the second one is a global variable that affects all sessions and needs a server restart to change its value. Both options cause…/doc/refman/5.1/en/innodb-locks-set.html. Conclusion MySQL uses REPEATABLE READ as the default isolation level so it…
Post: Faster Point In Time Recovery with LVM2 Snaphots and Binary Logs
February 23, 2012 By Leave a Comment
…rows affected (6.51 sec) Rows matched: 300024 Changed: 300024 Warnings: 0 With the last snapshot… saves it into a file specified as variable on the script. Below is the binary…mount /mysql/data [root@sb logs]# /etc/init.d/mysql start Starting MySQL (Percona Server) [ OK ] You should shutdown MySQL …
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 $_SESSION variable…previous changes. The problem is not actually with memcached or mysql, …for reliably locked simple single server installation, but not for …
Post: MySQL Server Variables - SQL layer or Storage Engine specific.
June 8, 2006 By 14 Comments
MySQL Server has tons of variables which may be adjusted to change behavior or for performance purposes. They are documented in the … and HEAP for in memory tables. So first MySQL versions did not bother naming variables with storage engines prefix. This is why… it mean MyISAM variables are not important ? Not really. You still have some tables in MyISAM format in “mysql” database. Plus HEAP…
Post: Can we improve MySQL variable handling ?
February 18, 2012 By 8 Comments
MySQL Settings (also known as Server Variables) have interesting property. When you set variable in running server this change is not persisted in any way and server… such change easily because MySQL Server does not seems to have an easy way to check what was the default value for given Server Variable…
Post: Percona Server 5.5.10 (Release Candidate)
April 4, 2011 By 4 Comments
… addition to MySQL 5.5.10 now being the base version, here are the changes that have been made since Percona Server beta… Biveinis) Variable Changes Old status variable innodb_row_lock_numbers was renamed to innodb_current_row_locks. (Yasufumi Kinoshita) Old system variable innodb_enable…
Post: Helgrinding MySQL with InnoDB for Synchronisation Errors, Fun and Profit
November 24, 2011 By 2 Comments
…MySQL server development: there is support for it in the MySQL Test Framework, DBQP, and the server…variables and LOCK_system_variables_hash. Deadlock is possible when one connection issues SHOW VARIABLES…
Post: How Percona diagnoses MySQL server stalls
March 3, 2011 By 6 Comments
… check for. VARIABLE=${VARIABLE:-Threads_connected} You need to change the threshold to 15, and the variable to …the disks are responding very well but the server is abusing them and overloading them. And …many things that can cause a stall in MySQL, and they usually begin microscopically and get…
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 only few of them are really important for most common workload. After you get these settings right other changes…
