Application compatibility levels in Db2 13
The application compatibility level of your applications controls the adoption and use of new capabilities and enhancements, and sometimes reduces the impact of incompatible changes. The advantage is that you can complete the Db2 13 migration process without the need to update your applications immediately.
After function level 500 or higher is activated, you can continue run applications with the features and behavior of previous versions or specific Db2 13 function levels.
You can change the application compatibility level for each application when you are ready for it to run with the features and behavior of a higher Db2 version or function level. The application compatibility level applies to most SQL statements, including data definition statements (such as CREATE and ALTER statements) and data control statements (such as GRANT and REVOKE statements).
The application compatibility of a package is initially set when you bind a package, based on the following values:
- The APPLCOMPAT bind option value, if specified.
- If the bind option is omitted, the APPLCOMPAT subsystem parameter.
For static SQL statements, the APPLCOMPAT column of the SYSIBM.SYSPACKAGE catalog table stores the application compatibility setting. This setting changes for the following reasons:
- You issue a REBIND command for the package and specify a different value for the APPLCOMPAT option. If you omit this option, the previous value for the package is used. If no previous value is available (such as for packages last bound before the introduction of application compatibility) the APPLCOMPAT subsystem parameter value is used.
- An automatic bind of the package occurs. The application compatibility is set to the previous value. If no previous value is available, the APPLCOMPAT subsystem parameter value is used.
For dynamic SQL statements, the CURRENT APPLICATION COMPATIBILITY special register stores the application compatibility setting. This setting changes for the following reasons:
- The special register is initialized to the application compatibility of the package, as described above.
- During execution of the package, SET CURRENT APPLICATION COMPATIBILITY statements can change the special register. The value must be equivalent to the APPLCOMPAT bind option for the package or lower, if the value is V12R1M500 or above.
For new installations, the default APPLCOMPAT subsystem parameter value is V13R1M500. However, you can specify a higher value. For migrated environments, the default value is the value from the migration input member.
Supported application compatibility levels in Db2 13
Db2 13 supports the following application compatibility levels in most contexts.
![Start of change](../../delta.gif)
![End of change](../../deltaend.gif)
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-
Compatibility with the behavior of the identified Db2 function level. For example,
V13R1M505
specifies compatibility with the highest available Db2 13 function level. The equivalent function level or higher must be activated.For the new capabilities that become available in each application compatibility level, see:
- SQL changes in Db2 13 application compatibility levels
- SQL changes in Db2 12 application compatibility levels
Tip:Extra program preparation steps might be required to increase the application compatibility level for applications that use data server clients or drivers to access Db2 for z/OS®. For more information, see Setting application compatibility levels for data server clients and drivers.
- V12R1
- Compatibility with the behavior of Db2 12 function level 500. This value has the same result as specifying
V12R1M500
. - V11R1
- Compatibility with the behavior of Db2 11 new-function mode.
- V10R1
- Compatibility with the behavior of DB2® 10 new-function mode. For more information, see V10R1 application compatibility level.
Example: V10R1 application compatibility
The following example shows the results of using a capability that is introduced in the application compatibility level V11R1, with application compatibility level set to V10R1. Assume that the APPLCOMPAT subsystem parameter value is V10R1. The example CREATE PROCEDURE statement does not specify the APPLCOMPAT keyword. In this example the CREATE TYPE statement is successful but the CREATE PROCEDURE statement results in SQL code -4743.
CREATE TYPE PHONENUMBERS AS VARCHAR(12) ARRAY ??(1000000??)
DSNT400I SQLCODE = 000, SUCCESSFUL EXECUTION
CREATE PROCEDURE FIND_CUSTOMERS(
IN NUMBERS_IN KRAMSC01.PHONENUMBERS,
IN AREA_CODE CHAR(3),
OUT NUMBERS_OUT KRAMSC01.PHONENUMBERS)
BEGIN
SET NUMBERS_OUT =
(SELECT ARRAY_AGG(T.NUM)
FROM UNNEST(NUMBERS_IN) AS T(NUM)
WHERE SUBSTR(T.NUM, 1, 3) = AREA_CODE);
END
DSNT408I SQLCODE = -4743, ERROR: ATTEMPT TO USE A FUNCTION WHEN THE
APPLICATION COMPATIBILITY SETTING IS SET FOR A PREVIOUS LEVEL
The APPLCOMPAT bind option value for the CREATE PROCEDURE statement is then set to V11R1 or higher and result of the statement is then successful.
CREATE PROCEDURE FIND_CUSTOMERS(
IN NUMBERS_IN KRAMSC01.PHONENUMBERS,
IN AREA_CODE CHAR(3),
OUT NUMBERS_OUT KRAMSC01.PHONENUMBERS)
APPLCOMPAT V11R1
BEGIN
SET NUMBERS_OUT =
(SELECT ARRAY_AGG(T.NUM)
FROM UNNEST(NUMBERS_IN) AS T(NUM)
WHERE SUBSTR(T.NUM, 1, 3) = AREA_CODE);
END
DSNT400I SQLCODE = 000, SUCCESSFUL EXECUTION