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table_open_cache

Linux system calls of MySQL process

Fri, 2019-03-15 17:06 — Shinguz
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system call
table_open_cache
table_definition_cache
system time
load average
open_files_limit
LimitNOFILE

We had the problem today that a MySQL Galera Cluster node with the multi-tenancy pattern caused a lot of system time (sy 75%, load average about 30 (you really must read this article by Brendan Gregg, it is w

Table open cache too small

Wed, 2015-07-15 06:04 — Shinguz
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fpmmm
table_open_cache
open_files_limit
table_cache
tuning
optimizing
configuration
parameter
variables
fpmmm Triggers and Rules
multi-tenant

The Table Open Cache (table_open_cache or old name table_cache) is a cache to store file handles for all threads. The actual value of cache entries can be seen with the global status of open tables (Open_tables).
Increasing table_open_cache increases the number of file descriptors (open_files_limit) that MySQL requires.

Could not increase number of max_open_files

Sun, 2014-12-28 15:37 — oli
Taxonomy upgrade extras: 
LimitNOFILE
open_files_limit
table_open_cache
file handles
General MySQL and MariaDB Questions
Hello all, on some Linux systems I get the following warning during my MySQL database start-up: 
[Warning] Buffered warning: Could not increase number of max_open_files to more than 1024 (request: 8192)
[Warning] Buffered warning: Changed limits: max_connections: 214 (requested 505)
[Warning] Buffered warning: Changed limits: table_cache: 400 (requested 512)

What does it mean and is that something I should care about?

Troubles with MySQL 5.5 on FreeBSD 9

Thu, 2012-03-29 11:55 — Shinguz
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mysql
table
temporary
table_open_cache
freebsd

FreeBSD 9 seems to have some troubles with MySQL 5.5.20. A customer has moved from MySQL 5.0 on Linux to MySQL 5.5 on FreeBSD 9. He experienced a lot of periodic slow downs on the new, much stronger, system which he has not seen on the old Linux box.

This slow downs were also shown in high CPU system time but we could not see any I/O going on.

When we looked into MySQL we have seen many threads in Opening tables state in the MySQL processlist.

How MySQL behaves with many schemata, tables and partitions

Wed, 2011-11-30 15:35 — Shinguz
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english
table
innodb
partition
myisam
schema
table_open_cache
table_definition_cache
open_files_limit
open_files
LimitNOFILE
multi-tenant

Introduction

Recently a customer claimed that his queries were slow some times and sometimes they were fast.

First idea: Flipping query execution plan caused by InnoDB could be skipped because it affected mainly MyISAM tables.

Second idea: Caching effects by either the file system cache caching MyISAM data or the MyISAM key buffer caching MyISAM indexes were examined: File system cache was huge and MyISAM key buffer was only used up to 25%.

I was a bit puzzled...

Configuration of MySQL for Shared Hosting

Fri, 2011-04-22 13:03 — Shinguz
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configuration
shared
hosting
hoster
setup
LimitNOFILE
table_open_cache
table_definition_cache
open_files_limit
multi-tenant

If you ask around about shared hosting setups with MySQL everybody is frightened. In fact it looks like shared hosting is one of the most difficult setups you can get.

The number of users is big, the number of tables huge and the load pattern is completely unpredictable and the queries often very, let us say: non-optimal.

Here one of the DBA wisdoms come into play: Controlling developers is like herding cats.

If you talk to the Shared MySQL Hoster they confirm that this setups are very demanding!

MySQL trouble shooting

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trouble shooting
open_files_limit
table_open_cache
LimitNOFILE
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