Changing COMPATIBLE Parameter and Data Guard

When you upgrade your Oracle Database, you should also decide how to raise the COMPATIBLE parameter. The considerations are the same when you use Data Guard, but the procedure is different.

Why

The main reason for raising COMPATIBLE is to enable new features.

Some new features are not backward compatible, e.g., blockchain tables. When someone introduces such features, the database:

  • is no longer backward compatible
  • can no longer be downgraded

When you upgrade, COMPATIBLE stays at the old setting. You need to actively raise it and allow the use of these new features. You are in total control.

Here is a video with more details about COMPATIBLE.

When

I recommend that you raise COMPATIBLE one or two weeks after the upgrade.

  • When you have seen that the new release works fine in production.
  • When you are confident that a database downgrade won’t be needed.

Raising COMPATIBLE requires a database restart, i.e., an outage. If such is unacceptable, you must raise COMPATIBLE as part of the upgrade. But be advised, it severely limits your fallback options.

AutoUpgrade does not change COMPATIBLE, unless you explicitly state it in the config file:

upg1.drop_grp_after_upgrade=yes
upg1.raise_compatible=yes

What

I recommend that you always set COMPATIBLE to the default of a database release:

  • 19.0.0
  • 21.0.0

If you only have non-CDBs then it might not matter much. But in a multitenant environment, having a uniform, COMPATIBLE setting is very beneficial. This allows PDBs to move between CDBs without problems.

How

You need to raise COMPATIBLE on all databases in your Data Guard configuration. The order is important:

  • First, standby databases (individual order is not important)
    STANDBY SQL> --Ensure redo apply is running
    STANDBY SQL> alter database recover managed standby database disconnect from session;
    STANDBY SQL> alter system set compatible='19.0.0' scope=spfile sid='*';
    STANDBY SQL> alter database recover managed standby database cancel;
    
    [oracle@standby]$ srvctl stop database -d $ORACLE_UNQNAME
    [oracle@standby]$ srvctl start database -d $ORACLE_UNQNAME -o mount
    
    STANDBY SQL> alter database recover managed standby database disconnect from session;
    
  • Last, primary database
    PRIMARY SQL> alter system set compatible='19.0.0' scope=spfile sid='*';
    
    [oracle@primary]$ srvctl stop database -d $ORACLE_UNQNAME
    [oracle@primary]$ srvctl start database -d $ORACLE_UNQNAME
    

Other Blog Posts in This Series

Further Reading