It is always a good idea to keep your databases' tables optimized. Fortunately, making this optimization is quite easy when using the phpMyAdmin. To perform the optimization,
1) Log in to Plesk.
2) Click on Databases & Select the Databases
2) Click on phpMyAdmin and select the database whose tables you wish to optimize.
A list with all the database's tables will appear. Tick the tables you wish to optimize, or simply click [Check All] to select all tables.
From the [With selected:] drop-down menu choose Optimize table. This will execute the OPTIMIZE TABLE SQL query on the selected tables and they will be updated and optimized.
