In linux server /tmp folder, we not sure when and why many of large files(.MYD and .MYI) created, it cause the web server slow down, temporary solution we used was restart server, but the problem still will occur sometime.

We use MySQL5.1 database. Storage engine is myISAM.

Any idea to troubleshoot this issue? Anyone here have experience same issue like this? Appreciated for any reply.

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  • A more complete listing of the files with date and time created would be helpful for you. These files with leading # are 'temporary' files created in support of your application. Something is preventing their typical removal in the normal course of using MySQL. Using MyISAM in 5.1 version could significantly increase performance by using INNODB storage engine to USUALLY reduce query execution time. Appropriate indexes must also be considered, for any data storage method to achieve high performance. Dec 15, 2021 at 13:28

1 Answer 1


The existence of those files has no impact on the performance of anything. It could impact lots of programs if you run out of disk space.

Such files are created temporarily during certain maintenance actions. When all goes well, those files will be deleted. You can remove them (if nothing like ALTER is busy running).

Since they are in /tmp, the next reboot (of Linux) will remove them (and anything else in /tmp).

You really should

  • Upgrade from the antique version 5.1, AND
  • Switch your tables to InnoDB.

If those came from a big "table" called "804" that is broken into lots of smaller tables, I must suggest that there are better ways to handle 'big' data. Most ways apply equally well to both MyISAM or InnoDB.

5.1 -> 5.5 -> 5.6 -> 5.7 -> 8.0 (MySQL)
MariaDB has an even longer chain of releases.

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