After migrating the Oracle Database Server to a new server with a higher version ( Oracle 19c instead of Oracle 12c) keeping the same Oracle Client 12c in the Automation Engine server, the WP / CP processes do not seem to free memory anymore until using all the available System Memory.
As a result, Jobs start to fail until it provokes a system standstill.
Memory Leak in the Oracle Client
Release : 12.x
Component : AUTOMATION ENGINE
The Oracle Client should always be in an equal or superior version to the Database Server as the Backwards Compatibility cannot be guaranteed.
Additionally, you will take advantage of possible Bug Fixes included into the latest Oracle Client version.
In order to fix the issue, upgrade Oracle Client to the latest version (in this case 19c) and restart the Automation Engine to start using the updated client.