Oracle Database Upgrade from 12.2 to 19c Using DBUA




1. Introduction

Upgrading Oracle databases is essential to ensure improved performance, security, and access to new features. Oracle Database 19c is a Long-Term Release (LTR) that provides enhanced stability, better optimizer performance, and extended support compared to Oracle 12c (12.2.0.1).

This document outlines the complete process of upgrading an Oracle 12c database to 19c using the Database Upgrade Assistant (DBUA). DBUA provides a guided, automated, and reliable approach to upgrade databases while minimizing manual effort and reducing risk.

The upgrade process includes pre-upgrade checks, environment validation, execution of upgrade using DBUA, and post-upgrade verification to ensure database integrity and performance.

2. Objective / Scope

Objective

  • Upgrade Oracle Database from 12.2.0.1 to 19c
  • Ensure minimal downtime and data integrity
  • Validate database readiness before upgrade
  • Perform upgrade using DBUA (GUI-based approach)
  • Execute post-upgrade validation and optimization steps

Scope

  • Source Database: Oracle 12c (12.2.0.1)
  • Target Database: Oracle 19c
  • Architecture: Multitenant (CDB with PDB)
  • Upgrade Method: DBUA (Database Upgrade Assistant)
  • Includes:
    • Pre-upgrade checks and fixups
    • Backup and recovery preparation
    • DBUA upgrade execution
    • Post-upgrade validation and cleanup

3. Environment Details

Parameter

Details

Hostname

srv5.cloudmap.in

Database Name

NEXUS

Source Version

12.2.0.1

Target Version

19c

Architecture

CDB (Single Instance)

PDB Name

APP_PDB

Source Oracle Home

/u01/app/oracle/product/12.2.0.1/db_1

Target Oracle Home

/u01/app/oracle/product/19.0.0/dbhome_1

Operating System

Linux x86 64-bit

Upgrade Method

DBUA

 

4. Prerequisites

Before starting the upgrade, ensure the following:

  • Full database backup is available
  • Backup of configuration files:
    • tnsnames.ora
    • listener.ora
    • sqlnet.ora
    • spfile / pfile
    • password file
  • Database is in ARCHIVELOG mode
  • Sufficient space in Fast Recovery Area (FRA)
  • Run Pre-Upgrade Information Tool (preupgrade.jar)
  • Execute:
    • preupgrade_fixups.sql
  • Ensure:
    • No critical errors in preupgrade logs
    • Required tablespace sizes are sufficient
  • Remove unnecessary objects:
    • Purge recycle bin
  • Gather statistics:
    • Dictionary statistics
    • Fixed object statistics

5. Implementation (Upgrade Steps)

5.1 Oracle 19c Software Availability

  • Verified that Oracle 19c Oracle Home is installed.

    /u01/app/oracle/product/19.0.0/dbhome_1

  • Oracle 19c Oracle Home is already installed and properly configured on my server. Hence, the upgrade process will proceed using the existing 19c software without any additional installation.
  • If not available, download and install Oracle 19c software before proceeding.

 

5.2  Source Database Validation

Verify oratab

 

Check PDBs

 

Check Compatibility



 

Database Version


 

 

 

Component Status

 

5.3 Backup Activities

Ensure complete backup before upgrade:

5.3.1 Database Backup

  • Confirm RMAN/full database backup is available.       -- I have it.

 

5.3.2 Network Configuration Backup

 

5.3.3 Parameter & Password Files Backup

 

5.4 Run Pre-Upgrade Tool

 

 

5.5 Review Pre-Upgrade Report




 


 

Observations

  • No mandatory actions.
  • Recommended:
    • Gather fixed object stats
    • Verify tablespace sizing
    • Timezone upgrade required post-upgrade

 

5.6 Tablespace Verification


 

** Tablespace Auto extend ON and max size also set, hence no action taken.

✔ No action required.

 

5.7 Initialization Parameters Check

  • No changes required based on preupgrade report.

 

 

5.8 Optimize Database Before Upgrade

 

5.9 Execute Pre-Upgrade Fixups

Oracle strongly recommends that you run the Pre-Upgrade Information Tool before starting the upgrade with DBUA. Although DBUA runs the Pre-Upgrade Information Tool as part of the pre-requisite checks, it is good practice to run the tool ahead of time in order to analyze the database and take actions that can decrease downtime for upgrading.

✔ Fixups executed successfully.

 

5.10 Archive Log & FRA Verification

✔ Sufficient space available.

 

5.11 Create Guaranteed Restore Point

*** NO need to enable Flashback Database from 11.2.0.1 onwards

*** Database MUST be in Archive Log mode

*** MUST NOT change the compatible parameter to higher version

 

✔ Restore point created successfully.

 

5.12 Set Environment for DBUA

Enable GUI



 

5.13 Run DBUA (Database Upgrade Assistant)

  • Launch DBUA:



 

Select the source database (12c) for upgrade or migration.
Choose database Nexus, provide SYSDBA credentials, and click Next.

 



Validate that all required PDBs are selected for upgrade and proceed by clicking Next.

 

DBUA automatically runs prerequisite checks.

Ensure all checks pass successfully and click Next.

 

Enable required upgrade options & Click Next to continue.

Select FRA (Fast Recovery Area) and confirm the previously created Guaranteed Restore Point for safe rollback if required.

 

DBUA updates the listener configuration:

  • Adds selected listener to target Oracle Home
  • Removes entry from source listener.ora
  • Reloads listener configuration in both source and target environments. Click Next.

Uncheck Enterprise Manager Database Express if not required and proceed by clicking Next.

 

Review the upgrade summary and analyze all configurations. Verify details before proceeding.

Click Finish to begin the upgrade process.

Monitor upgrade execution status.

 

After completion, verify:

  • Source and target database details
  • Upgrade success status
  • Total completion time

 

5.14 Post-Upgrade Verification

5.14.1 Verify oratab

 

5.14.2 Verify Database Version

 

5.14.3 Verify Timezone Version



 

5.14.4 Check Invalid Objects



 

 

 

5.14.5 Verify Component Status

 

5.15 Execute Post-Upgrade Fixups

 

5.16 Drop Restore Point

 

5.18 Update COMPATIBLE Parameter

Warning: If the value of COMPATIBLE parameter is changed to 19.0.0 then if for some reasons database needs to be downgraded to 12.2.0.1 the DBA would not have any option other than export/import to downgrade the database. But if this parameter is left unchanged for sometime to see how the database performs after upgrade then it is very easy and fast to downgrade the database if for some reason it is required to be downgraded.

 

If you change COMPATIBLE you can directly drop your restore points as they are useless. You can’t use Flashback Database to restore point back across a compatibility change of your database.

 

ALTER SYSTEM SET compatible='19.0.0' SCOPE=SPFILE;

  • Restart database after change.

6. Risks and Mitigation

⚠ Risks

  • Upgrade failure due to unresolved pre-check issues
  • Insufficient disk space or FRA size
  • Performance degradation after upgrade
  • Invalid objects or component failures
  • Data inconsistency in case of interruption

✅ Mitigation

  • Always perform upgrade in UAT/Test environment first
  • Take complete backup before upgrade
  • Use Guaranteed Restore Point for fallback
  • Resolve all preupgrade warnings and fixups
  • Monitor logs during DBUA execution
  • Perform thorough post-upgrade validation

7. Key Observations

  • Upgrade from 12.2.0.1 to 19c completed successfully using DBUA with minimal downtime
  • Pre-upgrade tool identified no critical issues; only recommended actions were present
  • Fixup scripts (preupgrade_fixups.sql) resolved required pre-upgrade conditions
  • Database remained in ARCHIVELOG mode, enabling safe upgrade and recovery options
  • Flashback Guaranteed Restore Point provided a reliable rollback mechanism
  • DBUA automatically handled:
    • Listener configuration updates
    • Environment switching between Oracle Homes
    • Component upgrades across CDB and PDB
  • Post-upgrade tasks ensured database stability and optimization

 

8. Benefits

·        Improved database performance and optimizer enhancements in 19c

·        Long-term support release (19c) ensures stability and fewer frequent upgrades

·        Enhanced security features and compliance capabilities

·        Better resource management in multitenant architecture (CDB/PDB)

·        Reduced manual effort due to automated DBUA upgrade process

·        Minimal impact on applications (no major structural changes required)

·        Built-in pre-checks reduce upgrade risks

10. Conclusion

The upgrade from Oracle 12c (12.2.0.1) to Oracle 19c using DBUA was successfully completed following a structured and validated approach. Pre-upgrade checks ensured readiness, while DBUA simplified the upgrade execution with minimal manual intervention.

Post-upgrade validation confirmed database integrity, component status, and performance stability. The database is now running on Oracle 19c, benefiting from improved performance, enhanced security, and long-term support

11. Future Enhancements

 Enable AutoUpgrade utility for future upgrades (automation)

 Implement performance tuning using AWR/ASH reports

 Upgrade Timezone version to latest (if pending)

 Enable Unified Auditing for better monitoring

 Integrate with:

  • Data Guard
  • RMAN catalog upgrades

 Automate:

  • Health checks
  • Post-upgrade validation scripts

 Evaluate 19c new features:

  • Real-Time Statistics
  • Automatic Indexing
  • SQL Plan Management improvements