# \#mysql-test

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## [How MySQL tables are opened? table\_definition\_cache, table\_open\_cache, .frm files and Data Dictionary: How are they related?](https://forums.percona.com/t/how-mysql-tables-are-opened-table-definition-cache-table-open-cache-frm-files-and-data-dictionary-how-are-they-related/16142)

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**Author:** [@vasanths20](https://forums.percona.com/u/vasanths20)\
**Replies:** 0\
**Last updated:** [June 15, 2022, 7:22am UTC](https://forums.percona.com/t/how-mysql-tables-are-opened-table-definition-cache-table-open-cache-frm-files-and-data-dictionary-how-are-they-related/16142 "2022-06-15T07:22:24Z")

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MySQL version: 5.7 Machine: Ubuntu 20.04 Recently, we were analysing the performance issues that can occur when increasing the number of tables in a schema. And during this, we came across 4 system variables that have i…