OCI-26040
Data block (file # string, block # string) is loaded on primary database using NOLOGGING option and cannot be read on a standby or after media recovery.
Cause
An attempt is made to access data in a block that is loaded without redo generation using the NOLOGGING/UNRECOVERABLE option.
Action
If this happens on a standby database, address this by using RMAN command "RECOVER DATAFILE <file #> NONLOGGED BLOCK". After the role change, the same command can be used at the primary database.