ORA-61877
True Cache recovery lags too far behind, exceeding string seconds.
Cause
A query cannot accept the most current data block because True Cache recovery lags too far behind, and must be aborted.
Action
Check V$DATABASE on the True Cache instance to see if OPEN_MODE is "READ ONLY WITH APPLY" and if CURRENT_SCN is advancing. Also, check if any error is present in V$TRUE_CACHE and V$DATAGUARD_STATUS on both the primary and True Cache instance. Restart True Cache if the error persists.