# Corruption and Repairs ==================================================================================== ### MySQL Check ``` mysqlcheck -options database ``` ##### MySQL Check Options:

-c	Checks tables for errors. It performs a `CHECK TABLE` operation on each table in the specified databases.
-r	Attempts to repair corrupted tables. It performs a `REPAIR TABLE` operation on each corrupted table.
-a	Analyzes tables for optimal performance. It performs an `ANALYZE TABLE` operation on each table.
-o	Optimizes tables to reduce fragmentation and reclaim unused space. It performs an `OPTIMIZE TABLE` operation on each table.
--databases db1 db2	Checks and repairs tables in multiple databases (`db1` and `db2`).
-A	Checks and repairs tables in all databases on the MySQL server.

------------------------------------------------------------------------------------------------------------------------------------------------ #### When to use mysqlcheck -r - **Table Corruption**: Use `mysqlcheck -r` (or `mysqlcheck --repair`) when you suspect or know that one or more tables in your MySQL database are corrupted or have crashed. - **Error Messages**: If MySQL reports errors such as "table is marked as crashed" or "table needs repair," `mysqlcheck -r` is a suitable approach to attempt repair. #### Best Practices and Considerations 1. **Backup**: Always make a backup of your databases before attempting any repairs. While `mysqlcheck -r` is generally safe, there is a small risk of data loss if the repair process encounters unexpected issues. 2. **Table Locking**: During repair, `mysqlcheck` will lock tables to ensure data consistency. Depending on the size and activity of your database, this can cause downtime or impact performance. ====================================================================================