ORA-61872
The string command in pluggable database string failed because some process is keeping a lock on it for too long. True cache will be restarted.
Cause
True Cache is trying to open, drop or rename a pluggable database but it is unable to get a lock in a reasonable time. This means that a previous redo marker to open, drop, close or rename the database did not finish in a reasonable time.
Action
Check alert log for additional information. The True Cache instance should be automatically restarted. If it failed, the instance will have to be manually restarted.