# Maintaining a Table

#### Scenarios

While working with a database, you do a lot of changes to tables such as inserting, updating and deleting data. This occupies disk space and deteriorates database performance. To handle this, periodic maintenance is required.

#### Functions

- Optimize

  Allows you to optimize tables using the OPTIMIZE TABLE statement and sort out fragmented files for later use.

  During the optimization, a read-only lock will be added to target tables. Therefore, optimizing tables during off-peak hours is recommended.

- Check

  Allows you to check whether there are errors in database tables using the CHECK TABLE statement. You can check a table with any of the following methods:

  - Check: Scan rows to verify that deleted links are valid. Alternatively, calculate a key checksum for the rows and verifies the validity using the obtained checksum.
  - Quick: Do not scan rows or check for incorrect links.
  - Fast: Check only tables that have not been closed properly.
  - Changed: Check only tables that have been changed since the last check or tables that have not been closed properly.
  - Extended: Search for keywords in each row.

    The CHECK TABLE statement adds a read-only lock to the table.

- Repair

  Allows you to use the REPAIR TABLE statement to repair possibly corrupted or incorrect tables. You can repair tables using any of the following three methods:

  - Repair: a simple repair, which repairs data and index files.
  - Quick: the quickest repair, which repairs only index files, but not data files.
  - Extended: the slowest repair, which creates indexes row by row to repair data and index files.
- Analyze

  Allows you to use the ANALYZE TABLE statement to analyze tables. During the analysis, read-only locks are added to tables. Tables can only be read during the analysis.

  Temporary files will be generated during table optimization. These files may occupy twice the disk space of the current table data.

#### Procedure

The following uses the Check operation as an example to explain how to maintain tables.

1. On the top menu bar, choose Database Management.
2. On the displayed Objects page, select Tables, locate the target table, and choose More > Maintain > Optimize in the Operation column.
3. In the displayed dialog box, click Yes.

Parent topic: Table Management