Since patch installation (SDM 17.3 RU22), the DB connections remain in open state until DB the application crashes and server is restarted.
Service Desk Manager 17.3RU22
This is a known issue and there's a defect associated with this DE 575770.
Need to apply patch 17.3RU23 or upgrade to 17.4RU1 to resolve the issue.
Note: 17.3 will be EOS very soon so it's recommended to upgrade to 17.4RU1.