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What is MySQL open files?
In this blog, we’ll look at a mystery around setting the MySQL open_file_limit variable in MySQL and Percona Server for MySQL. MySQL Server needs file descriptors to run. It uses them to open new connections, store tables in the cache, create temporary tables to resolve complicated queries and access persistent ones.
What is open_ files_ limit?
In MySQL, open_files_limit is the number of file descriptors available to mysqld from the operating system. At Bobcares, we often get requests to set MySQL variables, as a part of our Server Management Services.
What is Table_definition_cache?
The number of cached table definitions. See also: System Variables for MariaDB Enterprise Server 10.6, in 10.6 CS, in 10.5 ES, in 10.5 CS, in 10.4 ES, in 10.4 CS, in 10.3 ES, in 10.3 CS, in 10.2 ES, and in 10.2 CS.
How do you increase a hard limit?
To Increase the File Descriptor Limit (Linux)
- Display the current hard limit of your machine.
- Edit the /etc/security/limits.conf and add the lines: * soft nofile 1024 * hard nofile 65535.
- Edit the /etc/pam.d/login by adding the line: session required /lib/security/pam_limits.so.
How to check the open files limit in MySQL?
The open files limit can be checked on the mysql-client using show global varaibles like ‘%files%’ and then set global variable open_files_limit= .
How is the number of file descriptors open in MySQL determined?
The number of file descriptors mysqld can open simultaneously is defined by the configuration open_files_limit option. You would expect it to work like any other MySQL Server option: set in the configuration file, restart mysqldand use more or fewer descriptors.
How to get list of open files in MySQL?
Option 1: You can try running lsof on MySQL’s pid, piped to wc -l. These will give you the list of open files (including sockets, etc.; everything is a file in Unix/Linux). Be careful about this, since the number from ulimit -n is a total for the shell for all processes, and you don’t want to put it too high.