Cause: The primary database could not resolve a gap request from one or more standby databases. See the solution below.
Error solution: Check the StatusReport property of the primary database to see which standby database has an unresolvable gap. Copy the missing archived log files from either backups or from another database in the configuration that has the files to the standby database that is missing the files.
Database version: Oracle 11g Release 2 (11.2)