Symptoms
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Unable to access the Drupal website with the error:
500 error
Additional uncaught exception thrown while handling exception
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Some database operations via WordPress plugin may fail (for example, backup/restore with plugin WPVIVID)
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Going to Tools & Settings > System Updates, the Plesk System Updates page might fail to be accessed with the following error:
Server Error
500 PDOException
SQLSTATE[HY000]: General error: 2006 MySQL server has gone away
Cause
Insufficient value for max_allowed_packet or wait_timeout parameters.
Resolution
Increase max_allowed_packet or wait_timeout parameters according to the article How to set the value of max_allowed_packet or wait_timeout for MySQL on Plesk server?