Downgrading Database Without Executing catdwgrd.sql
My Database was upgraded to 12.1.0.2 but due to performance issues, application team requested us to downgrade the database to 11.2.0.4 (previous version).
The easiest way I could think of was to flashback the database using the restore point I created before upgrading the database to 12c
Below statements should hold true to flashback the database to the earlier version.
1) We have previous version binaries still present
2) A guarantee restore point created on earlier version before the upgrade is done
3) The compatible parameter is not changed.
Steps to downgrade the database from 12.1.0.2 to 11.2.0.4
From 12.1.0.2 binaries
Check the restore point if exists
SQL> select NAME,SCN,TIME from v$restore_point;
NAME SCN TIME
-------------------------------------------- ---------------------
BEFORE_UPGRADE 1.5096E+13 22-JUN-17 01.55.58.000000000 PM
Crosscheck if the compatible parameter is not changed
SQL> show parameter compatible
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
compatible string 11.2.0.4.0
noncdb_compatible boolean FALSE
Mount the database
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Database mounted.
Flashback database to the restore point created
SQL> FLASHBACK DATABASE TO RESTORE POINT BEFORE_UPGRADE;
Flashback complete.
Alert log shows below
Database mounted in Exclusive Mode
Lost write protection disabled
Completed: ALTER DATABASE MOUNT
Mon Jun 26 10:59:03 2017
FLASHBACK DATABASE TO RESTORE POINT BEFORE_UPGRADE
Mon Jun 26 10:59:05 2017
Flashback Restore Start
Mon Jun 26 10:59:40 2017
Flashback Restore Complete
Flashback Media Recovery Start
Started logmerger process
Mon Jun 26 10:59:41 2017
Parallel Media Recovery started with 12 slaves
Flashback Media Recovery Log /opt/app/prod1/oraflsh01/PROD1/archivelog/2017_06_22/o1_mf_1_1236_dnrds518_.arc
Mon Jun 26 10:59:42 2017
Incomplete Recovery applied until change 15095662683591 time 06/22/2017 13:56:00
Mon Jun 26 10:59:42 2017
Flashback Media Recovery Complete
Completed: FLASHBACK DATABASE TO RESTORE POINT BEFORE_UPGRADE
Once flashback completes shutdown the database
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
Now mount the database from older binaries, [in our case 11.2.0.4], set your environment to point to 11.2.0.4 binaries
SQL> startup mount
ORACLE instance started.
Total System Global Area 2.1379E+10 bytes
Fixed Size 2262656 bytes
Variable Size 3221227904 bytes
Database Buffers 1.8119E+10 bytes
Redo Buffers 36073472 bytes
Database mounted.
Open Resetlogs
SQL> alter database open resetlogs;
Database altered.
Now check the DB version, it should show 11.2.0.4
SQL> select comp_name, version, status from dba_registry;
COMP_NAME
--------------------------------------------------------------------------------
VERSION STATUS
------------------------------ --------------------------------------------
Oracle XML Database
11.2.0.4.0 VALID
Oracle Expression Filter
11.2.0.4.0 VALID
Oracle Rules Manager
11.2.0.4.0 VALID
COMP_NAME
--------------------------------------------------------------------------------
VERSION STATUS
------------------------------ --------------------------------------------
Oracle Workspace Manager
11.2.0.4.0 VALID
Oracle Database Catalog Views
11.2.0.4.0 VALID
Oracle Database Packages and Types
11.2.0.4.0 VALID
COMP_NAME
--------------------------------------------------------------------------------
VERSION STATUS
------------------------------ --------------------------------------------
JServer JAVA Virtual Machine
11.2.0.4.0 VALID
Oracle XDK
11.2.0.4.0 VALID
Oracle Database Java Packages
11.2.0.4.0 VALID
