Oracle Database Upgrade: 12c → 19c using DBUA (Real DBA Checklist)

 Oracle Database upgrade from 12c to 19c using DBUA (Database Upgrade Assistant).

Sharing a practical DBA checklist that can help Oracle professionals during upgrade activities 👇
✅ PRE-UPGRADE TASKS (Critical Phase)
🔹 1. Download Oracle 19c software from Oracle Support
🔹 2. Ensure full database backup is available (RMAN recommended)
📁 Backup & move required files:
tnsnames.ora
listener.ora
sqlnet.ora
pfile / spfile
password file (orapwd)
🔹 3. Install & unzip Oracle 19c software in a new ORACLE_HOME
🔹 4. Run Pre-Upgrade Tool (preupgrade.jar)
🔹 5. Review preupgrade log and generated scripts:
preupgrade_fixups.sql
postupgrade_fixups.sql
🔹 6. Check minimum tablespace size requirements
🔹 7. Gather dictionary statistics

EXEC DBMS_STATS.GATHER_DICTIONARY_STATS;
🔹 8. Purge recycle bin

PURGE DBA_RECYCLEBIN;
🔹 9. Run preupgrade_fixups.sql to fix issues
🔹 10. Verify archive log destination size
🔹 11. Create Guaranteed Restore Point

CREATE RESTORE POINT pre_upgrade GUARANTEE FLASHBACK DATABASE;
🔄 UPGRADE PHASE (Using DBUA)
🔹 12. Start DBUA from Oracle 19c home:

$ORACLE_HOME/bin/dbua
🔹 13. Follow GUI steps:
Select database
Choose base location
Start upgrade process
🔹 14. Monitor upgrade progress & logs
✅ POST-UPGRADE TASKS (Validation Phase)
🔹 15. Run postupgrade_fixups.sql
🔹 16. Recompile & verify invalid objects

@?/rdbms/admin/utlrp.sql
🔹 17. Drop restore point

DROP RESTORE POINT pre_upgrade;
🔹 18. Update COMPATIBLE parameter

ALTER SYSTEM SET compatible='19.0.0' SCOPE=SPFILE;
🔹 19. Verify database components

SELECT comp_name, status FROM dba_registry;
🔹 20. Update TNS entries in 19c ORACLE_HOME
🔹 21. Configure password file (orapwd)
🔹 22. Take full post-upgrade backup
💡 Key Takeaways
✔ Pre-checks are the most important part of any Oracle upgrade
✔ Always keep rollback & restore strategy ready
✔ Validate database health after upgrade
✔ 19c is the Long-Term Support (LTS) version – highly recommended
🤝 For Oracle DBAs