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Applying PSU and RU Patches Safely in Oracle Databases

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Applying PSU and RU Patches
  • User AvatarPradip
  • 28 Oct, 2025
  • 0 Comments
  • 3 Mins Read

Applying PSU and RU Patches Safely in Oracle Databases

Keeping your Oracle Database environment updated is critical for maintaining security, stability, and performance. Oracle regularly releases Patch Set Updates (PSU) and Release Updates (RU) to fix bugs, address vulnerabilities, and enhance functionality.

However, applying these patches requires careful planning and execution to avoid downtime, data loss, or service disruption. In this blog, we’ll walk you through how to safely apply PSU and RU patches in Oracle environments — step by step.

Understanding PSU and RU

Before applying patches, it’s important to understand the difference between PSU and RU:

  • PSU (Patch Set Update):
    These are quarterly patches that include security and critical bug fixes. PSUs are conservative and less invasive, making them suitable for stable production systems.

  • RU (Release Update):
    RUs are more comprehensive, containing all PSU fixes plus additional improvements, new features, and optimizer changes. These are ideal for environments where continuous feature updates are acceptable.

Both are cumulative — meaning newer versions include previous fixes — but RUs are the preferred standard starting from Oracle 12.2 and later.

Step 1: Pre-Patching Preparations

Applying patches safely begins with thorough preparation:

  1. Identify the Current Version:

    SELECT * FROM v$version;

    or

    $ORACLE_HOME/OPatch/opatch lsinventory

  2. Download the Correct Patch:
    Get the latest PSU or RU patch from My Oracle Support (MOS). Always verify platform and database version compatibility.

  3. Check OPatch Utility Version:
    Ensure your OPatch tool is up to date:

    $ORACLE_HOME/OPatch/opatch version

  4. Take a Full Backup:
    Use RMAN to take a full database backup or a snapshot if the environment is virtualized.

    RMAN> BACKUP DATABASE PLUS ARCHIVELOG;

  5. Check for Conflicts:
    Run a conflict check before patching:

    opatch prereq CheckConflictAgainstOHWithDetail -phBaseDir <patch_directory>

  6. Stop Database and Listeners (If Required):
    For database patches, ensure you stop all Oracle services cleanly:

    srvctl stop database -d <dbname>
    lsnrctl stop

Step 2: Applying the Patch

Once pre-checks are complete, proceed with the patching:

  1. Unzip the Patch:

    unzip pXXXXXX_190000_Linux-x86-64.zip -d /u01/patches/

  2. Apply the Patch using OPatch:

    cd /u01/patches/XXXXXX
    opatch apply

  3. For RAC or Grid Infrastructure:
    Use opatchauto to simplify patching across nodes:

    opatchauto apply /u01/patches/XXXXXX

  4. Monitor the Log File:
    Check the patch logs under $ORACLE_HOME/cfgtoollogs/opatch/ to confirm successful patching.

Step 3: Post-Patch Steps

After patching, always perform the following validation steps:

  1. Startup Database and Services:

    srvctl start database -d <dbname>
    lsnrctl start

  2. Execute Post-Installation SQL Scripts (if applicable):
    Some patches require SQL scripts to be run as SYSDBA:

    sqlplus / as sysdba
    SQL> @?/rdbms/admin/catbundle.sql psu apply

  3. Verify Patch Application:

    opatch lsinventory

  4. Check Database Functionality:
    Test basic operations, connectivity, and application performance.

  5. Gather Updated Statistics:
    Run stats gathering jobs to ensure the optimizer works with the latest changes.

Step 4: Rollback Plan

Even with all precautions, patch failures can occur. Always have a rollback strategy:

  • Restore from RMAN backup if the patch causes issues.

  • Use opatch rollback -id <Patch_ID> to revert the patch.

  • Re-validate system stability before bringing it back into production.

Best Practices for Safe Patching

  • Apply patches first on a test or staging environment before production.

  • Maintain a patching calendar aligned with Oracle’s quarterly Critical Patch Updates (CPU).

  • Keep documentation of all patch activities — patch ID, date, nodes affected, and verification results.

  • Ensure adequate disk space and FRA space before patching.

  • In RAC setups, apply patches node by node to minimize downtime.

Final Thoughts

Patching is a crucial part of Oracle DBA operations that ensures your database remains secure, compliant, and stable. By following structured pre-checks, backup strategies, and post-validation steps, you can apply PSU and RU patches safely without impacting production.

Regular patching not only keeps your systems protected but also improves performance and compatibility with Oracle’s evolving ecosystem.

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