Non-CDB to CDB/PDB Migration Runbook: Mandatory AutoUpgrade Conversion Before Oracle 26ai

Executive Summary & Architectural Context

ith the release of Oracle Database 26ai, Oracle Corporation officially removed all support for legacy Non-CDB (Non-Container Database) architecture. While Oracle Database 19c permitted non-CDB deployments as a legacy fallback, Oracle 26ai exclusively runs on the Multitenant Architecture (CDB/PDB).

To upgrade a legacy Oracle 19c non-CDB to Oracle 26ai, DBAs cannot perform a direct in-place upgrade on a non-CDB instance. The non-CDB database must first be converted into a Pluggable Database (PDB) and plugged into a target Container Database (CDB).

<div class="process-flow">
  <div class="process-step">
    <div class="step-number">1</div>
    <div class="step-title">Source Pre-Checks</div>
    <div class="step-desc">Run AutoUpgrade -mode analyze on 19c Non-CDB source database.</div>
  </div>
  <div class="process-arrow">➔</div>
  <div class="process-step">
    <div class="step-number">2</div>
    <div class="step-title">Target CDB Creation</div>
    <div class="step-desc">Provision empty 19c/26ai CDB shell with matching character set (AL32UTF8).</div>
  </div>
  <div class="process-arrow">➔</div>
  <div class="process-step">
    <div class="step-number">3</div>
    <div class="step-title">AutoUpgrade Plugin</div>
    <div class="step-desc">AutoUpgrade executes noncdb_to_pdb.sql conversion and plugs PDB into target CDB.</div>
  </div>
  <div class="process-arrow">➔</div>
  <div class="process-step">
    <div class="step-number">4</div>
    <div class="step-title">PDB Compilation</div>
    <div class="step-desc">Open PDB in READ WRITE, recompile invalid objects via utlrp.sql, and verify datapatch.</div>
  </div>
</div>

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🛠️ Step 1: Pre-Migration Prerequisites & Character Set Audit

Before attempting non-CDB to PDB conversion, ensure the source non-CDB and target CDB satisfy mandatory architectural compatibility rules:

1. Character Set Alignment: The target CDB’s NLS_CHARACTERSET MUST be a superset of or identical to the source non-CDB. Oracle strongly recommends AL32UTF8.
2. Time Zone Version: The target CDB’s time zone file version must be equal to or higher than the source database.
3. Database Options: Installed options (e.g., Spatial, OLAP, Multimedia) in the source non-CDB must exist in the target CDB root (CDB$ROOT).

Run the following SQL query on both the source Non-CDB and target CDB to audit compatibility:

-- Audit Database Character Set, National Character Set, and Time Zone Version
SELECT property_name, property_value 
FROM database_properties 
WHERE property_name IN ('NLS_CHARACTERSET', 'NLS_NCHAR_CHARACTERSET', 'DST_PRIMARY_TT_VERSION');

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📝 Step 2: AutoUpgrade Plugin Configuration File Creation

The modern Oracle AutoUpgrade utility automates the entire non-CDB to PDB conversion workflow via the target_cdb and plugin_filename directives.

Create an AutoUpgrade configuration file (/u01/app/oracle/cfg/noncdb_to_pdb.cfg) on your database server:

# Global AutoUpgrade Parameters
global.autoupg_log_dir=/u01/app/oracle/cfg/logs

# Job 1: Non-CDB (PROD19) to PDB (PDB_PROD19) Conversion in Target CDB (CDB26)
upg1.dbname=PROD19
upg1.start_time=IMMEDIATE
upg1.source_home=/u01/app/oracle/product/19.0.0/dbhome_1
upg1.target_home=/u01/app/oracle/product/26.0.0/dbhome_1
upg1.sid=PROD19
upg1.target_cdb=CDB26
upg1.target_pdb_name=PDB_PROD19
upg1.target_db_start_mode=READ WRITE
upg1.upg_err_action=abort
upg1.restoration=YES

💡 Tip: Setting restoration=YES automatically creates a guaranteed restore point (GRP) prior to conversion, enabling instant fallback if storage or plugin errors occur.

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🚀 Step 3: Executing Pre-Checks & Non-CDB Conversion

1. Run AutoUpgrade Pre-Checks (Analyze Mode)

Execute AutoUpgrade in analyze mode to validate dictionary sanity, undo mode, and tablespace encryptions without modifying database files:

java -jar /u01/app/oracle/product/26.0.0/dbhome_1/rdbms/admin/autoupgrade.jar \
  -config /u01/app/oracle/cfg/noncdb_to_pdb.cfg \
  -mode analyze

Review the generated HTML report located in /u01/app/oracle/cfg/logs/PROD19/100/prechecks/PROD19_prechecks.html. Resolve any FAILURE or WARNING items (such as stale optimizer stats or pending material views).

2. Execute Non-CDB Conversion (Deploy Mode)

Once pre-checks pass cleanly, launch AutoUpgrade in deploy mode to execute the non-CDB to PDB plugin conversion:

java -jar /u01/app/oracle/product/26.0.0/dbhome_1/rdbms/admin/autoupgrade.jar \
  -config /u01/app/oracle/cfg/noncdb_to_pdb.cfg \
  -mode deploy

AutoUpgrade automatically executes the following actions:

1. Creates a Guaranteed Restore Point (AUTOUPGRADE_GRP_PROD19).
2. Shuts down the non-CDB source database (PROD19) cleanly.
3. Generates the PDB manifest XML file (/u01/app/oracle/cfg/logs/PROD19_describe.xml).
4. Plugs PROD19 as PDB_PROD19 into target CDB26.
5. Executes noncdb_to_pdb.sql to re-align dictionary views with CDB$ROOT.
6. Opens PDB_PROD19 in READ WRITE mode and runs datapatch to align SQL patch levels.

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🔍 Step 4: Post-Migration Validation & PDB Health Check

After AutoUpgrade completes with status FINISHED, connect to the target Container Database (CDB26) to verify PDB plugin status:

-- Connect to target CDB as SYSDBA
SQL> CONNECT / AS SYSDBA;

-- 1. Verify PDB open status and restricted mode
SELECT name, open_mode, restricted, total_size/1024/1024/1024 AS size_gb 
FROM v$pdbs 
WHERE name = 'PDB_PROD19';

-- Expected Output:
-- NAME         OPEN_MODE   RESTRICTED   SIZE_GB
-- ------------ ----------- ------------ ----------
-- PDB_PROD19   READ WRITE  NO           450.25

-- 2. Inspect PDB Plugin Violations
SELECT type, cause, message, status 
FROM pdb_plug_in_violations 
WHERE name = 'PDB_PROD19' AND status != 'RESOLVED';

-- Expected Output: 0 rows selected (or harmless WARNINGs for OPTION mismatch)

If pdb_plug_in_violations displays unresolved ERROR items (e.g. ORA-65126), execute utlrp.sql inside the PDB to recompile invalid objects:

ALTER SESSION SET CONTAINER = PDB_PROD19;
@?/rdbms/admin/utlrp.sql

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📚 Official Documentation & Technical References

• Oracle Database 23ai/26ai Upgrade Guide — Official Oracle Database Upgrade Documentation
• Oracle AutoUpgrade Utility Guide — Official Guide on AutoUpgrade Syntax and Configuration Parameters
• ORACLE-BASE: AutoUpgrade Download and Installation — Tim Hall’s Guide to AutoUpgrade Workflows

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Need expert assistance migrating legacy Non-CDB databases to Multitenant PDBs or upgrading to Oracle 26ai? Contact our Database Specialists or explore our Enterprise Health Audits.