6 Downgrading Oracle Database to an Earlier Release

6.1 Supported Releases for Downgrading Oracle Database

You can downgrade both major releases and patchset releases, based on the original Oracle Database release from which the database was upgraded. Major release downgrades are supported back to Oracle Database 11g Release 2 (11.2.0.2) and subsequent 11.2 releases, and Oracle Database 11g Release 1 (11.1.0.7). Patchset downgrades are supported back to Oracle Database release 11.2 patchsets, except release 11.2.0.1.

Table 6-1 provides a summary of releases supported for downgrading. When using this table, also read about compatibility in "Checking for Incompatibilities When Downgrading Oracle Database."

The following recommendations for earlier supported releases affect downgrading for Oracle Database:

• This release includes multitenant architecture, which provides features for a multitentant container database (CDB) and pluggable databases (PDBs). Therefore, setting the compatible initialization parameter to the highest level after upgrading to this release prevents the capability to downgrade.

• This release contains a new object privilege, READ, in addition to SELECT. After you downgrade:

  • If you have the SELECT and READ object privileges, the READ privilege is removed.

  • If you only had the READ object privilege, then this is transformed into the SELECT object privilege.

  See Oracle Database Security Guide for information about the READ and SELECT object privileges.

• The earliest release that you can downgrade back to is Oracle Database release 11.1.0.7. Because the minimum compatibility for Oracle Database 12c is 11.0, after you upgrade to release 12.1, the compatibility must be set to at least 11.0. Once compatibility is set, this changes the on-disk structure of the database and enables new features that are controlled by the compatible setting. Therefore, downgrade to a release earlier than 11.1.0.7 is no longer an option.

• If Oracle XML DB was not present in the database to be upgraded, then Oracle XML DB is uninstalled during the downgrade. For example, if you did not install Oracle XML DB with Oracle Database 11g Release 2 (11.2), then when upgrading to Oracle Database 12c, Oracle XML DB is installed because it is included with this release. During a downgrade back to Oracle Database 11g Release 2 (11.2), Oracle XML DB is removed.

• During upgrade to Oracle Database 12c, the Database (DB) Control repository is removed. If you downgrade, you must reconfigure the Database (DB) Control to use it again in the earlier, downgraded release. See "Saving Oracle Enterprise Manager Database Control Configuration and Data."

• Downgrade is not supported for Oracle Enterprise Manager. You must reconfigure Oracle Enterprise Manager controls if you downgrade to an earlier supported release. See "Restoring Oracle Enterprise Manager after Downgrading Oracle Database."

• Oracle Clusterware for Oracle Database 12c does not support downgrading to Oracle Database release 10.2 and release 11.1 on Windows. A fresh install is required for releases earlier than release 11.2.

6.2 Checking for Incompatibilities When Downgrading Oracle Database

Check the compatibility level of your database to see if the database might have incompatibilities that prevent you from downgrading. If the compatibility level of your Oracle Database 12c database is 12.1.0, then you are not able to downgrade.

If you are downgrading to Oracle Database 11g Release 2 (11.2.0.2), Oracle Database 11g Release 2 (11.2.0.3), or Oracle Database 11g Release 2 (11.2.0.4), then the COMPATIBLE initialization parameter must be set to 11.2.0 or lower. Downgrading to release 11.2.0.1 is not supported.

If you are downgrading to Oracle Database 11g Release 1 (11.1.0.7), then the COMPATIBLE initialization parameter must be set to 11.1.0 or lower. Only downgrading to release 11.1.0.7 is supported for Oracle Database 11g Release 1.

6.3 Performing a Full Backup Before Downgrading Oracle Database

Oracle strongly recommends that you perform a full backup of your Oracle Database 12c database before you downgrade to a supported earlier releases.

6.4 Performing Required Pre-Downgrade Steps for Oracle Database

Before downgrading to the earlier release from which you upgraded, you must complete required preparation. For example, you may need to determine if components in the database must be disabled first.

To prepare for downgrading:

1. If you are downgrading a CDB or unplugging and downgrading a PDB in Oracle Database release 12.1.0.2, then you must first apply PSU4 (patch set update 4). You obtain PSU4 and any required set of additional fixes by going to My Oracle Support at https://support.oracle.com/. The patch set information and link is contained in MOS Note 756671.1. Search for 756671.1 in the general search box on the Patches and Updates page. This is a requirement before you can downgrade.

2. If you are downgrading to Oracle Database release 11.1, then before starting the downgrade procedures, ensure that you know the password for any newly-created database links. These are database links that you may have created while running releases 11.2 or 12.1. Knowing the database link password is necessary because you will need to reset the database link password after downgrading to Oracle Database release 11.1. See "Issue with Password for Database Links After Downgrading" for more information.

3. If you have enabled Oracle Database Vault on your database, then disable Oracle Database Vault before downgrading the database.

   To find if Oracle Database Vault is enabled, query the V$OPTION dynamic view as follows:

   Enter Oracle Database Vault in the case shown in this query. If the output is TRUE, then Oracle Database Vault is enabled, so you must disable it. See Oracle Database Vault Administrator's Guide for instructions.

4. If your database uses Oracle Label Security and you are downgrading to release 11.2 or earlier, then run the Oracle Label Security (OLS) preprocess downgrade olspredowngrade.sql script in the new Oracle Database 12c Oracle home. You do not need to run olspredowngrade.sql if you are downgrading release 12.1.0.2 to release 12.1.0.1.

   Important:

   Running the olspredowngrade.sql script before downgrading is mandatory for downgrading from Oracle Database 12c to database release 11.2 (and earlier) in databases that use Oracle Label Security and Oracle Database Vault.

   1. To find out if Oracle Label Security is enabled, query the V$OPTION dynamic view as follows:

      SQL> SELECT VALUE FROM V$OPTION WHERE PARAMETER = 'Oracle Label Security';
      

   2. Run the olspredowngrade.sql script.

      SQL> @ORACLE_HOME/rdbms/admin/olspredowngrade.sql
      

      See Oracle Label Security Administrator's Guide for more information.

5. If you have enabled unified auditing, then optionally back up and purge the unified audit trail.

   1. Find if unified audit records exist.

   2. Back up the existing audit data to a table. For example:

      SQL> CREATE TABLE UA_DATA AS (SELECT * FROM V$UNIFIED_AUDIT_TRAIL);
      

   3. Clean up the audit trail.

      EXEC DBMS_AUDIT_MGMT.CLEAN_AUDIT_TRAIL(audit_trail_type => DBMS_AUDIT_MGMT.AUDIT_TRAIL_UNIFIED, use_last_arch_timestamp => FALSE);
      

6. If you previously installed a recent version of the time zone file and used the DBMS_DST PL/SQL package to upgrade TIMESTAMP WITH TIME ZONE data to that version, then install the same version of the time zone file in the release to which you are downgrading. If after the database upgrade, you had used DBMS_DST to upgrade the TIMESTAMP WITH TIME ZONE data to the latest version of the time zone file, then install this latest version time zone file in the release to which you are downgrading. This ensures that your TIMESTAMP WITH TIME ZONE data is not logically corrupted during retrieval.

   To find which timze zone file version your database is currently using, query V$TIMEZONE_FILE as follows:

   SQL> select * from  V$TIMEZONE_FILE;
   

   Copy the time zone files from the current Oracle home to the Orache home to which you are downgrading. For example, after you see the results of your query, you might choose from the following:

   %ORACLE_HOME%\oracore\zoneinfo\timezlrg_18.dat
   %ORACLE_HOME%\oracore\zoneinfo\timezone_18.dat
   

   See Oracle Database Globalization Support Guide for more information on upgrading time zone files, and Oracle Database PL/SQL Packages and Types Reference for information about the DBMS_DST package.

7. If you set the ORA_TZFILE environment variable to the full path name of the time zone file when you upgraded to Oracle Database 12c, then you must unset it if you subsequently downgrade your database.

   Two time zone files are included in the Oracle home directory:

   • The default time zone file, which is for the database server, at

     $ORACLE_HOME/oracore/zoneinfo/timezonelrg.dat
     

   • A smaller time zone file, which is typically used for clients, at

     $ORACLE_HOME/oracore/zoneinfo/timezone.dat
     

   If you do not unset the ORA_TZFILE variable, then connecting to the database using the smaller time zone file might produce the following errors:

   SP2-1503: Unable to initialize Oracle call interface
   SP2-0152: ORACLE may not be functioning properly
   

   See Oracle Database Globalization Support Guide for more information about date and time data types and time zone support.

8. Optional: If you are downgrading to Oracle Database 11g Release 1 (11.1.0.7) and you have Oracle Application Express in your database, then you must copy the apxrelod.sql file from the Oracle Database 12c ORACLE_HOME/apex/ directory to a directory outside of the Oracle home, such as a temporary directory on your system.

   Make a note of the new location of this file. You need this later in the procedure.

9. If you have created objects based on fixed objects, then drop these objects to avoid possible ORA-00600 errors. You can re-create these objects after the downgrade.

10. If you have Oracle Enterprise Manager configured in your database, then drop the Enterprise Manager user:

    DROP USER sysman CASCADE;
    

    Note:

    After this step, MGMT* synonyms may be invalid. You must reconfigure Oracle Enterprise Manager to use any Oracle Enterprise Manager controls in the downgraded database.

6.5 Downgrading a CDB or Non-CDB Oracle Database

Oracle provides a procedure for downgrading your Oracle Database 12c database to a supported major release or a relevant patchset upgrade. If you are downgrading from release 12.1.0.2 or higher to release 12.1.0.1, you can downgrade all databases in a multitenant container database (CDB) or one pluggable database (PDB) within a CDB. Oracle Database releases earlier than Oracle Database 12c did not use multitenant architecture. See "Downgrading a Single Pluggable Oracle Database (PDB)" for the procedure for downgrading one PDB.

The procedure in this section assumes that you understand "Supported Releases for Downgrading Oracle Database."

To downgrade the database, whether a CDB or not, to an earlier supported release:

1. Log in to the system as the owner of the Oracle Database 12c Oracle home directory.

2. At a system prompt, change to the ORACLE_HOME/rdbms/admin directory, where ORACLE_HOME is the Oracle home on your system.

   Note:

   If you are downgrading a cluster database, then shut down the database completely and change the CLUSTER_DATABASE initialization parameter to FALSE. After the downgrade, you must set this parameter back to TRUE.

3. Using SQL*Plus, connect to the database instance as a user with SYSDBA privileges.

   sqlplus sys as sysdba
   Enter password: password
   

4. Log in to the system as the owner of the Oracle home under the new Oracle Database 12c.

5. From the ORACLE_HOME/rdbms/admin directory, start SQL*Plus.

6. Connect to the database to be upgraded using an account with DBA privileges:

   CONNECT / AS SYSDBA
   

7. Start the instance in downgrade mode by issuing the following SQL*Plus command for your Oracle Database instance type. You may be required to use the PFILE option to specify the location of your initialization parameter file.

   For Non-CDB instances:

   SQL> startup downgrade pfile=pfile_name
   

   For CDB instances:

   SQL> startup downgrade pfile=pfile_name
   SQL> alter pluggable database all open downgrade;
   

   Specify the location of your initialization parameter file PFILE. See Oracle Database Administrator's Guide for information about specifying initialization parameters at startup and the initialization parameter file.

8. Optional: If you are downgrading a non-CDB, you can set the system to spool results to a log file so you can track the changes and issues. (A CDB automatically spools output to the catcon_logs; therefore, you can skip this step for a CDB.)

   SQL> SPOOL downgrade.log
   

9. Run catdwgrd.sql.

   For a non-CDB:

   SQL> @catdwgrd.sql
   

   For a CDB:

   $ORACLE_HOME/perl/bin/perl $ORACLE_HOME/rdbms/admin/catcon.pl -d 
    $ORACLE_HOME/rdbms/admin -e -b catdwgrd -l <output directory> -r 
    catdwgrd.sql
   

   In the CDB example catcon.pl is run with catdwgrd. You first start PERL. The -d parameter tells catcon.pl where to find catdwgrd. The -l parameter specifies the output directory for log files (instead of writing to the rdbms/admin directory). You must use the -r parameter to run the two scripts together.

   Note:

   • You must use the version of the catdwgrd.sql script included with Oracle Database 12c.

   • You must run catdwgrd.sql in the Oracle Database 12c environment.

   • You must specify the -r parameter in order to run the two scripts together at the same time.

   • The catdwgrd.sql script downgrades all Oracle Database components in the database to the supported major release or patch release from which you originally upgraded.

   If you encounter any problems when you run the catdwgrd.sql script, or any of the scripts in the remaining steps, then correct the causes of the problems and rerun the script. You can rerun any of the scripts described in this chapter as many times as necessary.

   Caution:

   If the downgrade for a component fails, then an ORA-39709 error is displayed and the SQL*Plus session terminates without downgrading the Oracle Database data dictionary. All components must be successfully downgraded before the Oracle Database data dictionary is downgraded. You must identify and fix the problem before rerunning the catdwgrd.sql script.

10. For non-CDB only, turn off the spooling of script results to the log file:

    SQL> SPOOL OFF
    

    Then, check the spool file and verify that there were no errors generated during the downgrade. You named the spool file in Step 8 and the suggested name was downgrade.log. Correct any problems you find in this file and rerun the downgrade script if necessary.

    Note:

    If you want to save the results of the first time you ran the downgrade script, then before you rerun it be sure to rename downgrade.log to something else.

11. Shut down the instance:

    SQL> SHUTDOWN IMMEDIATE
    

12. Exit SQL*Plus.

13. If your operating system is Linux or UNIX, then change the following environment variables to point to the directories of the release to which you are downgrading:

    • ORACLE_HOME

    • PATH

    You should also check that your oratab file and any client scripts that set the value of ORACLE_HOME point to the downgraded Oracle home.

    See Oracle Database Installation Guide for your operating system for information about setting other important environment variables on your operating system.

14. If your operating system is Windows, then complete the following steps:

    1. Stop all Oracle services, including the OracleServiceSID Oracle service of the Oracle Database 12c database, where SID is the instance name.

       For example, if your SID is ORCL, then enter the following at a command prompt:

       C:\> NET STOP OracleServiceORCL
       

       See Oracle Database Platform Guide for Microsoft Windows for more information about stopping Oracle services on Windows.

    2. Delete the Oracle service at a command prompt by issuing the ORADIM command.

       For example, if your SID is ORCL, then enter the following command:

       C:\> ORADIM -DELETE -SID ORCL
       

    3. Create the Oracle service of the database that you are downgrading at a command prompt using the ORADIM command.

       C:\> ORADIM -NEW -SID SID -INTPWD PASSWORD -MAXUSERS USERS
       -STARTMODE MANUAL -PFILE ORACLE_HOME\DATABASE\INITSID.ORA
       

       See Oracle Database Platform Guide for Microsoft Windows for information about administering an Oracle Database instance using ORADIM. The syntax for ORADIM includes the following variables:

       Variable	Description
       SID	Same SID name as the SID of the database being downgraded.
       PASSWORD	Password for the database instance. This is the password for the user connected with SYSDBA privileges. The -INTPWD option is not required. If you are prompted for a password, use the password for the standard user account for this Windows platform.
       USERS	Maximum number of users who can be granted SYSDBA and SYSOPER privileges.
       ORACLE_HOME	Oracle home directory of the database to which you are downgrading. Ensure that you specify the full path name with the -PFILE option, including drive letter of the Oracle home directory. See Oracle Database Administrator's Guide for information about specifying initialization parameters at startup and the initialization parameter file.

       
       

       For example, if your SID is ORCL, your PASSWORD is TWxy5791, the maximum number of USERS is 10, and the ORACLE_HOME directory is C:\ORANT, then enter the following command:

       C:\> ORADIM -NEW -SID ORCL -INTPWD TWxy5791 -MAXUSERS 10
            -STARTMODE MANUAL -PFILE C:\ORANT\DATABASE\INITORCL.ORA
       

       Note:

       The ORADIM command prompts you for the password for the Oracle home user account. You can specify other options using ORADIM.

       You are not required to change any Windows Registry settings when downgrading a database. The ORADIM utility makes all necessary changes automatically.

15. Restore the configuration files (for example, parameter files, password files, and so on) of the release to which you are downgrading.

    If this is an Oracle RAC database, execute the following command to return the database to single instance mode:

    SET CLUSTER_DATABASE=FALSE
    

    Note:

    If you are downgrading a cluster database, then perform this step on all nodes on which this cluster database has instances configured. Set the CLUSTER_DATABASE initialization parameter to FALSE. After the downgrade, you must set this initialization parameter back to TRUE.

    See Oracle Real Application Clusters Administration and Deployment Guide for information about initialization parameter use in Oracle RAC.

16. At a system prompt, change to the ORACLE_HOME/rdbms/admin directory of the earlier release to which you are downgrading.

17. Start SQL*Plus and connect to the database instance as a user with SYSDBA privileges.

    For a non-CDB:

    SQL> CONNECT / AS SYSDBA
    SQL> STARTUP UPGRADE
    

    For a CDB:

    connect / as sysdba
    startup database mount;
    alter database open upgrade;
    alter pluggable database all open upgrade;
    

18. Optional: For a non-CDB, set the system to spool results to a log file to track changes and issues. This step is not needed for a CDB.

    SQL> SPOOL reload.log
    

19. Run catrelod.sql.

    For a non-CDB:

    SQL> @catrelod.sql
    

    For a CDB:

    $ORACLE_HOME/perl/bin/perl catcon.pl -n 1 -e -b catrelod -d '''.''' catrelod.sql
    

    The catrelod.sql script reloads the appropriate version for each of the database components in the downgraded database.

20. If you are downgrading to Oracle Database 11g Release 1 (11.1.0.7) and you have Oracle Application Express in your database, then change to the directory to which you had copied the apxrelod.sql script. Manually reload Oracle Application Express by running the apxrelod.sql script:

    SQL> @apxrelod.sql
    

    Running the apxrelod.sql script avoids package APEX_030200.WWV_FLOW_HELP being INVALID due to the following error:

    PLS-00201: identifier 'CTX_DDL' must be declared
    

21. If you had turned spooling on for a non-CDB, now turn off the spooling of script results to the log file:

    SQL> SPOOL OFF
    

    Then, check the spool file and verify that the packages and procedures compiled successfully. Correct any problems you find in this log file and rerun the appropriate script if necessary.

22. Shut down and restart the instance for normal operation:

    SQL> SHUTDOWN IMMEDIATE
    SQL> STARTUP
    

    You might be required to use the PFILE option to specify the location of your initialization parameter file. See Oracle Database Administrator's Guide for information about specifying initialization parameters at startup and the initialization parameter file.

23. Perform this step if the database is configured for Oracle Label Security.

    1. Copy the olstrig.sql script from the Oracle home under Oracle Database 12c to the Oracle home of the release to which the database is to be downgraded.

    2. From the Oracle home of the release you are downgrading to, run olstrig.sql to re-create DML triggers on tables with Oracle Label Security policies:

       SQL> @olstrig.sql
       

       See Oracle Label Security Administrator's Guide for more information about Oracle Label Security.

24. Run the utlrp.sql script.

    For a non-CDB:

    SQL> @utlrp.sql
    

    For a CDB run catcon.pl to invoke utlrp.sql to recompile any remaining stored PL/SQL and Java code. Use the following syntax:

    $ORACLE_HOME/perl/bin/perl catcon.pl -n 1 -e -b utlrp -d '''.''' utlrp.sql
    

    The utlrp.sql script recompiles all existing PL/SQL modules that were previously in an INVALID state, such as packages, procedures, types, and so on. The log file utlrp0.log is generated with the results of the recompilations.

25. Exit SQL*Plus.

26. If you are downgrading a cluster database, then you must run the following command to downgrade the Oracle Clusterware database configuration:

    $ srvctl downgrade database -d db-unique-name -o oraclehome -t to_version
    

    [where db-unique-name is the database name (not the instance name), oraclehome is the location of the old Oracle home for the downgraded database, and to_version is the database release to which the database is downgraded. (For example: 11.2.0.3.0.)]

    Note:

    Execute this command from the current Oracle Database 12c Oracle home, not from the Oracle home to which the database is being downgraded.

Your database is now downgraded.

6.6 Downgrading a Single Pluggable Oracle Database (PDB)

If you are downgrading the latest release of Oracle Database 12c, you can downgrade one PDB without downgrading the whole CDB. For example, you can unplug a PDB from a release 12.1.0.2 CDB, downgrade it, and then plug it in to a release 12.1.0.1 CDB or convert the database to a standalone database.

The procedure in this section assumes that you understand "Supported Releases for Downgrading Oracle Database."

Step 1   Downgrade the PDB

In this step you downgrade the PDB to release 12.1.0.1.

1. Start up the release 12.1.0.2 PDB in DOWNGRADE mode. The CDB can be in normal mode when you do this.

   SQL> alter pluggable database CDB1_PDB1 open downgrade;
   

2. Downgrade the PDB by running catdwgrd, which in this example is PDB1.

   Run catdwgrd as follows:

   $ORACLE_HOME/perl/bin/perl $ORACLE_HOME/rdbms/admin/catcon.pl -d
    $ORACLE_HOME/rdbms/admin -n 1 -l <output directory> -e -b catdwgrd -c 'PDB1'
    catdwgrd.sql
   

   In the example catcon.pl is run with catdwgrd. You first start PERL. The -d parameter tells catcon.pl where to find catdwgrd. The -l parameter specifies the output directory for log files (instead of writing to the rdbms/admin directory). You must use the -r parameter to run the two scripts together at the same time.

3. Close the PDB.

Step 2   Unplug the PDB from the CDB

In this step you unplug the downgraded PDB from the release 12.1.0.2 CDB.

1. Connect to the 12.1.0.2 CDB.

2. Close the PDB to be unplugged.

   SQL> alter pluggable database PDB1 close;
   

3. Unplug the downgraded 12.1.0.1 PDB.

   SQL> alter pluggable database PDB1 unplug into 'path/PDB1.xml';
   

   You will see Pluggable database altered.

Step 3   Plug in the Downgraded 12.1.0.1 PDB

In this step you plug the downgraded 12.1.0.1 PDB into the 12.1.0.1 CDB. To do this, you must create the PDB in this CDB. In this example, we create PDB1.

1. Connect to the 12.1.0.1 CDB.

2. Plug in the 12.1.0.1 PDB.

   SQL> create pluggable database PDB1 using 'path/PDB1.xml';
   

   You will see Pluggable database created.

3. Open the PDB in upgrade mode in order to run the scripts shown in the subsequent steps in this procedure.

   SQL> alter pluggable database PDB1 open upgrade;
   

4. Connect to the PDB:

   SQL> alter session set container=PDB1;
   

5. Run catrelod in the PDB:

   SQL> @$ORACLE_HOME/rdbms/admin/catrelod.sql
   

   The catrelod.sql script reloads the appropriate version for each of the database components in the downgraded database.

6. Run utlrp in the PDB:

   SQL> @$ORACLE_HOME/rdbms/admin/utlrp.sql
   

   The utlrp.sql script recompiles all existing PL/SQL modules that were previously in an INVALID state, such as packages, procedures, types, and so on.

6.7 Post-Downgrade Tasks for Oracle Database Downgrades

Additional tasks may be required after downgrading an Oracle database due to changes that affect compatibility, components, and supported protocols.

This section contains the following topics:

• Oracle XML DB Authentication Recommendations for an Oracle Database Downgrade

• Re-creating the Network Listener When Downgrading to Release 11.1.0.7

• Re-enabling Oracle Database Vault after Downgrading Oracle Database

• Restoration of the Configuration for Oracle Clusterware

• Restoring Oracle Enterprise Manager after Downgrading Oracle Database

• Restoring Oracle Application Express to the Earlier Version

ORACLE_HOME/bin/emca -restore db

ORACLE_HOME/bin/emca -restore db -cluster

ORACLE_HOME/bin/emca -restore asm

ORACLE_HOME/bin/emca -restore asm -cluster

ORACLE_HOME/bin/emca -restore db_asm

ORACLE_HOME/bin/emca -restore db_asm -cluster

6.8 Troubleshooting the Downgrade of Oracle Database

Oracle provides troubleshooting information for issues that may occur when downgrading Oracle Database. This section contains known errors that may occur and corresponding workarounds when needed.

This section contains the following topics:

• Oracle Multimedia Downgrade and imrelod.sql Script Error

• Oracle Database Vault and dvrelod.sql Script Error

• Downgrading Grid Infrastructure Standalone (Oracle Restart) After Successful or Failed Upgrade

• Issue with Downgrading Oracle ACFS and Oracle Grid Infrastructure

• Issue with Password for Database Links After Downgrading