Before you upgrade, review compatibility between your earlier release Oracle Database and the new Oracle Database release as part of your upgrade plan.
Understanding Oracle Database Compatibility
If new features are incompatible with your earlier release, then Database compatibility can cause issues.
Databases from different releases of Oracle Database software are compatible if they support the same features, and if those features perform the same way. When you upgrade to a new release of Oracle Database, certain new features can make your database incompatible with your earlier release.
Your upgraded database becomes incompatible with your earlier release under the following conditions:
A new feature stores any data on disk (including data dictionary changes) that cannot be processed with your earlier release.
An existing feature behaves differently in the new environment as compared to the old environment.
When to Set the COMPATIBLE Initialization Parameter in Oracle Database
Oracle recommends increasing the
COMPATIBLE parameter only after you have completed testing the upgraded database.
After the upgrade is complete, you can increase the setting of the
COMPATIBLE initialization parameter to the maximum level for the new Oracle Database release. However, after you increase the
COMPATIBLE parameter, you cannot subsequently downgrade the database.
The COMPATIBLE Initialization Parameter in Oracle Database
Review to understand how to set the COMPATIBLE initialization parameter for non-CDB and multitenant architecture containers.
Oracle Database enables you to control the compatibility of your database with the COMPATIBLE initialization parameter.
Understanding the COMPATIBLE Initialization Parameter
In Oracle Database 19c, when the COMPATIBLE
initialization parameter is not set in your
parameter file, the
parameter value defaults to
19.0.0 If you do not set the
initialization parameter to
19.0.0, then you cannot use the
new Oracle Database 19c features, because your
upgraded database is not running in the required
setting for Oracle Database 19c features.
Due to changes in internal SQL identifier and
schema object name restrictions, you can
experience an initial delay for any process where
the database runs a Java stored procedure directly
or indirectly in the database server after you
setting. When you increase the Oracle Database
COMPATIBLE parameter to 12.2.0 or
later from a
earlier than 12.2.0, and the database runs a Java
stored procedure, the database performs a "name
translation" operation. This operation can require
a few minutes to complete. You should expect this
delay the first time the database runs a Java
stored procedure after you increase the
compatibility parameter. This delay for the
database to perform the name translation occurs
only during the first Java process call.
Before upgrading to Oracle Database 19c, you must set the
COMPATIBLEinitialization parameter to at least
11.2.0, which is the minimum setting for Oracle Database 19c.
The compatible parameter must be at least 3 decimal numbers, separated by periods. For example:
SQL> ALTER SYSTEM SET COMPATIBLE = '19.0.0' SCOPE=SPFILE;
Oracle recommends that you only raise the
COMPATIBLEparameter after you have thoroughly tested the upgraded database.
After you increase the
COMPATIBLEparameter, you cannot downgrade the database, and you cannot flash back to restore points.
If you are upgrading from Oracle Database release 11.2, then you must set the compatible value to at least 11.2.0. You must do this at the time of the upgrade. Do not make this change until you are ready to upgrade, because a downgrade back to an earlier compatibility level is not possible after you raise the COMPATIBLE initialization parameter value.
Oracle Database Administrator’s Guide for information about managing initialization parameters
Rules for COMPATIBLE Parameter Settings in Multitenant Architecture
The COMPATIBLE parameter of the container database (CDB) affects the COMPATIBLE parameter settings of pluggable databases (PDBs) plugged into that container database. Review the following scenarios that occur when you plug in a PDB to a CDB:
PDB COMPATIBLE equal to
CDB$ROOTCOMPATIBLE parameter setting.
Result: No change to the PDB COMPATIBLE parameter setting.
PDB COMPATIBLE is lower than
CDB$ROOTCOMPATIBLE parameter setting.
Result: The PDB COMPATIBLE parameter is increased automatically to the same COMPATIBLE parameter setting as
CDB$ROOT. After you plug in the PDB, you cannot downgrade the PDB to an earlier release.
PDB COMPATIBLE is higher than
CDB$ROOTCOMPATIBLE parameter setting.
Result: The PDB cannot be plugged in. Only PDBs with a COMPATIBLE parameter setting equal to or lower than
CDB$ROOTcan be plugged in to the CDB.
Values for the COMPATIBLE Initialization Parameter in Oracle Database
Review to find the default, minimum, and maximum values for the COMPATIBLE initialization parameter for Oracle Database 19c.
Default and Minimum COMPATIBLE Parameter Values
The COMPATIBLE parameter should not be changed for an RU or an RUR, either for CDB or Non-CDB instances. The following table lists the default and minimum values for the COMPATIBLE parameter in Oracle Database 19c, compared to earlier releases supported for direct upgrade:
Table 1-2 The COMPATIBLE Initialization Parameter
|Oracle Database Release||Default Value||Minimum Value|
|Oracle Database 19c||
Oracle Database 12c Release 2 (12.2)
Oracle Database 12c Release 1 (12.1)
Oracle Database 11g Release 2 (11.2)
About Downgrading and Compatibility for Upgrading Oracle Database
Before upgrading to Oracle Database 19c, you must set the COMPATIBLE initialization parameter to at least
After upgrading to Oracle Database 18c, you can set the COMPATIBLE initialization parameter to match the release number of the new release. Doing so enables you to use all features of the new release, but prevents you from downgrading to your earlier release. Only a subset of Oracle Database 18c features are available while the
COMPATIBLE initialization parameter is set to a lower value.
After you increase the COMPATIBLE parameter, the database cannot be downgraded.
How the COMPATIBLE Initialization Parameter Operates in Oracle Database
COMPATIBLE initialization parameter enables or disables Oracle Database features based on release compatibility
COMPATIBLE initialization parameter operates in the following way:
COMPATIBLEinitialization parameter enables or disables the use of features, to help protect your existing application use of data.
If you run an Oracle Database 12c database with the
COMPATIBLEinitialization parameter set to
11.2.0, then the database software generates database structures on disk that are compatible with Oracle Database Release 11g release 2 (11.2). If you try to use features that are part of a later release of Oracle Database, and make the database incompatible with the
COMPATIBLEinitialization parameter, then an error occurs. However, new features are enabled that do not create changes on disk that are incompatible with Oracle Database Release 11g release 2.
If you make changes to the database that make the database incompatible with the
COMPATIBLEinitialization parameter setting you want to use, then the database does not start, and initialization terminates in an error. If this happens, then you must set the
COMPATIBLEinitialization parameter to an appropriate value for the database.
Oracle Database Concepts for more information about database structures