How to fix Joomla jtablesession::store failed DB error

The last time I saw jtablesession::store failed error it was caused by some bad data in jos_session table in Joomla database. Here's how you can fix it given that the table name is jos_session:

1. Go to your hosting cPanel, DirectAdmin, etc.
2. Go to phpMyAdmin
3. Select your joomla website database
4. Check the table jos_session in the table list
5. At the bottom of the table list from the drop-down list select the option repair the table

More info here.