ORA-61868
True Cache entry corresponding to the hash ID string not found in a LOG_ARCHIVE_DEST_n parameter.
Cause
A True Cache server tried to read some data block from a primary database but the primary server was not able to find a connection string to connect back to the True Cache.
Action
Verify if the primary database has a LOG_ARCHIVE_DEST_n parameter defined for the True Cache server. If not, restart the True Cache server.