ORA-38856: cannot mark instance UNNAMED_INSTANCE_2 (redo thread 2) as enabled

When you clone a Instance from a DB which is non rac but a clone of RAC

Eg:

PROD--RAC
DEV-Non Rac cloned from PROD

No You want to clone DEV to TEST.

After restoring the DB from the backup of DEV when you issue the below command

SQL>Alter database open resetlogs;

*ERROR at line 1:ORA-38856: cannot mark instance UNNAMED_INSTANCE_2 (redo thread 2) as enabled


This is because of the RAC component which is still valid in Source.

Solution:

1) Solution:-Edit the init.ora file and put the parameter “_no_recovery_through_resetlogs”.Startup mount the instance.SQL>startup mount.SQL>alter database open resetlogs;


2)On the Source (DEV)
sqlplus / as sysdba

sql>dbms_registry.invalid("RAC");

SQL>exit;

Now take a backup of database and then clone TEST from this backup.



Thanks,
Sandarsh