Maintaining a Table
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.
During the optimization, a read-only lock will be added to target tables. Therefore, optimizing tables during off-peak hours is recommended.
- 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: 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.
Temporary files will be generated during table optimization. These files may occupy twice the disk space of the current table data.
The following uses the Check operation as an example to explain how to maintain tables.
- On the top menu bar, choose Database Management.
- On the displayed Objects page, select Tables, locate the target table, and choose More > Maintain > Optimize in the Operation column.Figure 1 Maintaining a table
- In the displayed dialog box, click Yes.Figure 2 Optimizing tables