Downgrading Oracle Clusterware to an Earlier Release

After a successful or a failed upgrade, you can downgrade Oracle Clusterware to the previous release.

Before downgrading, review Patching, Upgrading, and Downgrading Oracle Grid Infrastructure with FIPS 140.3. When the stated compatibility conditions apply, first disable FIPS on all nodes, update and verify the GPnP profile is signed using RSA-SHA1, and only then begin rollback.

About Oracle Grid Infrastructure Downgrades

Understand the process and impacts of Oracle Grid Infrastructure downgrades.

Downgrading Oracle Clusterware restores the Oracle Clusterware configuration to the state it was in before the Oracle Grid Infrastructure upgrade. Any configuration changes you performed during or after the Oracle Grid Infrastructure upgrade are removed and cannot be recovered.

To restore Oracle Clusterware to the previous release, use the downgrade procedure for the release to which you want to downgrade.

Note:

You can downgrade the cluster nodes in any sequence. You can downgrade all cluster nodes except one, in parallel. You must downgrade the last node after you downgrade all other nodes.
When downgrading after a failed upgrade, if the rootcrs.sh or rootcrs.bat file does not exist on a node, then instead of executing the script, use the command perl rootcrs.pl . Use the Perl interpreter located in the Oracle Home directory.

Options for Oracle Grid Infrastructure Downgrades

You can downgrade Oracle Grid Infrastructure to earlier releases after a successful or a failed upgrade.

Downgrade options include the following earlier releases:

Oracle Grid Infrastructure downgrade to Oracle Grid Infrastructure 21c.
Oracle Grid Infrastructure downgrade to Oracle Grid Infrastructure 19c.

Note:

When you downgrade Oracle Grid Infrastructure to an earlier release, for example from Oracle Grid Infrastructure 26ai to Oracle Grid Infrastructure 21c, the later release RAC databases already registered with Oracle Grid Infrastructure will not start after the downgrade.

Restrictions for Oracle Grid Infrastructure Downgrades

Review the following information for restrictions and changes for downgrading Oracle Grid Infrastructure installations.

You can only downgrade to the Oracle Grid Infrastructure release you upgraded from. For example, if you upgraded from Oracle Grid Infrastructure 19c to Oracle Grid Infrastructure 26ai, you can only downgrade to Oracle Grid Infrastructure 19c.

Downgrading Oracle Grid Infrastructure

Use this procedure to downgrade Oracle Grid Infrastructure after a successful upgrade.

As the root user, use the command syntax rootcrs.sh -downgrade from 26ai Grid home to downgrade Oracle Grid Infrastructure on all nodes, in any sequence. For example:
```
# $ORACLE_HOME/crs/install/rootcrs.sh -downgrade
```
Run this command from a directory that has write permissions for the Oracle Grid Infrastructure installation user. You can run the downgrade script in parallel on all cluster nodes, but one.
Downgrade the last node after you downgrade all other nodes:
```
# $ORACLE_HOME/crs/install/rootcrs.sh -downgrade
```
Set previous release Grid home as the active Oracle Clusterware home:
1. On any of the cluster member nodes where the rootupgrade script has run successfully, log in as the Oracle Grid Infrastructure installation owner.
2. Use the following command to start the installer, where the path you provide for ORACLE_HOME is the location of the home directory from the earlier Oracle Clusterware installation.
```
$ cd $ORACLE_HOME/oui/bin 
$ ./runInstaller -nowait -waitforcompletion -ignoreSysPrereqs -updateNodeList -silent CRS=true ORACLE_HOME=pre-upgrade-grid-home "CLUSTER_NODES=node1,node2,node3"
```
  pre-upgrade-grid-home is the previous release Grid home.
As the root user, start the Oracle Clusterware stack on all nodes from previous release Grid home.
```
# crsctl start crs
```

Downgrading Oracle Grid Infrastructure when Upgrade Fails

If upgrade of Oracle Grid Infrastructure fails before CVU post upgrade checks succeed, then you can run gridSetup.sh and downgrade Oracle Grid Infrastructure to the earlier release.

Run this procedure to downgrade Oracle Clusterware only when the upgrade fails before CVU post upgrade checks succeed.

From the later release Grid home, run gridSetup.sh in silent mode, to downgrade Oracle Clusterware:

$ /u01/app/23.0.0/grid/gridSetup.sh -silent -downgrade [-nodes] nodes_to_be_downgraded 
[-oldHome] pre-upgrade-grid-home 
[-configmethod] root | sudo [-sudopath path_to_sudo_program]
[-sudousername sudoer_name]

Note:

You can downgrade the cluster nodes in any sequence.

Downgrading Oracle Grid Infrastructure Using Online Terminate Upgrade

If upgrade of Oracle Grid Infrastructure fails before setting the active version of Oracle Clusterware, then follow these steps to downgrade Oracle Grid Infrastructure to the earlier release.

Run this procedure to downgrade Oracle Clusterware only when the upgrade fails before root script runs the crsctl set crs activeversion command on the last node. Use this procedure for downgrading Oracle Grid Infrastructure if there is a need to avoid downtime of the whole cluster. This procedure downgrades the cluster to the previous release. Because Oracle ASM and database operations are limited in this state, it is required to downgrade the cluster as soon as possible. Complete the downgrade of Oracle Grid Infrastructure as per the procedure documented in Downgrading Oracle Grid Infrastructure after Upgrade Fails.

Shut down the Oracle Grid Infrastructure stack on the node that you are downgrading.
```
crsctl stop crs
```
Run the following command on all cluster nodes on which Oracle Grid Infrastructure is running, but not on the node that you are downgrading.
```
clscfg -nodedowngrade -h hostname
```
hostname is the name of the node that you are downgrading.
From the later release Grid home, run the following command on all cluster nodes, which are successfully upgraded, to downgrade Oracle Clusterware.
```
rootcrs.sh -downgrade -online
```
If rootcrs.sh is not present, then use rootcrs.pl.
Start Oracle Grid Infrastructure stack on all the nodes from the earlier release Grid home.
```
crsctl start crs
```
Note:
You can downgrade the successfully upgraded cluster nodes in any sequence.
On the last node where the Grid Infrastructure stack from the earlier release is running, unset the Oracle ASM rolling migration mode as follows:
1. Log in as grid user, and run the following command as SYSASM user on the Oracle ASM instance:
```
SQL> ALTER SYSTEM STOP ROLLING MIGRATION;
```