MyISAM
lastmod 2024-11-29created 2024-11-292 edits
MyISAM was the default storage engine of the MySQL relational database management system before version 5.5. It was based on the older ISAM code but had many more useful extensions. MyISAM's biggest shortcoming was its lack of transaction support. MySQL 5.5 and later versions switched to the InnoDB engine to ensure referential integrity constraints and higher concurrency.
Each MyISAM table was stored on disk in three files. These files begin with the same name as the table and have an extension indicating the file type. MySQL uses a .frm file to store the table definition, but this file is not part of the MyISAM engine; it is part of the server. The data file has the .MYD (MYData) extension, and the index file has the .MYI (MYIndex) extension. In other words, each table has the following files.
- .frm - table definition file
- .MYD - data file
- .MYI - index file