COMPATIBLE

Property	Description
Parameter type	String
Syntax	COMPATIBLE = release_number
Default value	11.0.0
Modifiable	No
Range of values	10.0.0 to default release
Basic	Yes
Real Application Clusters	Multiple instances must have the same value.

COMPATIBLE allows you to use a new release of Oracle, while at the same time guaranteeing backward compatibility with an earlier release. This is helpful if it becomes necessary to revert to the earlier release.

This parameter specifies the release with which Oracle must maintain compatibility. It allows you to take advantage of the maintenance improvements of a new release immediately in your production systems without testing the new functionality in your environment. Some features of the release may be restricted.

When using a standby database, this parameter must have the same value on both the primary and standby databases.

Note:

1. The COMPATIBLE initialization parameter needs a special mention when upgrading a database (say, from 10.2 to 11.1) because it has consequences if the database needs to be downgraded. Once the database has been upgraded, the COMPATIBLE parameter has been set to 11.1, and the database has been restarted, then the datafiles, controlfiles and online logfiles are updated to the new version. This in turn will prevent the database from being downgraded in the future. Any attempt to downgrade the database will report an error:

SQL> STARTUP DOWNGRADE;

ORACLE instance started.

Total System Global Area 436207616 bytes

Fixed Size 2029528 bytes

Variable Size 327157800 bytes

Database Buffers 104857600 bytes

Redo Buffers 2162688 bytes

ORA-00201: control file version 11.1.0.0.0

incompatible with ORACLE version 10.2.0.0.0

ORA-00202: control file: '/u01/oradata/B920/

control01.ctl'

When this error occurs the only way to downgrade the database is to restore the database from the backup taken before the database was upgraded or to use any alternate strategies in place like Streams, Data Guard or Export/Import. Because of the inability to downgrade the database once it has been opened with the new COMPATIBLE parameter, it is recommended to leave the parameter set to the 10.2 value until the newly upgraded database performance and functionality is acceptable. At that time, the COMPATIBLE parameter can be reset to the new, higher version and any new features that require COMPATIBLE to be 10.1 or higher can begin to be used.

2. Query for the current value of the parameter

select name, value, isdefault, isses_modifiable, issys_modifiable,

isinstance_modifiable, isdeprecated, description

from v$parameter where upper(name) = ‘COMPATIBLE’;

NAME	VALUE	IS DEFAULT	ISSES_ MODIFIABLE	ISSYS_ MODIFIABLE	ISINSTANCE_ MODIFIABLE	IS DEPRECATED	DESCRIPTION
compatible	10.2.0.1	FALSE	FALSE	FALSE	FALSE	FALSE	Database will be completely compatible with this software version

Oracle initializatoin parameters

Last updated: April 22, 2009.