ORA-01571: redo version [string] incompatible with ORACLE version [string]
Cause: This software version can not read the current redo logs, and either crash recovery is required or there are offline database files that need media recovery. If a file name is listed then it needs media recovery.
Action: Shutdown and startup using the compatible software. Do any required media recovery, and open the database. Shutdown and then startup using current software. If the file is going to be dropped then take it offline with the DROP option to skip this check.