Oracle recommended that the following tasks be performed after the upgrade of Oracle RDBMS to 12c.

1. Backup the database – make a full backup of the system after upgrade.
2. Execute postupgrade_fixups.sql – The Database Upgrade Assistance BDUA executes this script as a normal upgrade process.  Execute this script anytime or after manual upgrade process.  This script generates three types of upgrade info for administrator.
   1. General Warning.
   2. Errors
3. Gather Fixed Objects statistics – Execute DBMS_STATS.GATHER_FIXED_OBJECTS_STATS post upgrade and after the database has been running in normal operation for a few days. This can improve overall performance of the database.
4. Reset Passwords to Enforce Case-Sensitivity – Execute DBMS_VERIFIER.EXPIRE_ACCOUNTS_WITHOUT_LATEST_VERIFIER procedure to force users which are not using the latest password restrictions to reset password on next logon.
5. Set Threshold Values for Tablespace Alerts – After upgrade tablespace alerts are shutoff. Id tablespaces which need to have alerts set and set them.
6. Migrate from rollback segments to Automatic Undo Mode – If migrated database was before 11g, you were using rollback segments, you must migrate database to Automatic Undo to take advantage of increased performance.
7. Migrate Tables from LONG to LOB – LOB of type (BFILE,BLOB, CLOB, NCLOB) have a lot of advantage over LONG. Use ALTER TABLE command to convert LONG to CLOB and LONG RAW to BLOB.

Larry Catt

OCP