Choosing a simulation database
When you create and run a stub to virtualize calls from z/OS® programs to Db2®, the data is stored in a simulation database. You can choose to use the integrated database of Rational® Integration Tester, a Db2® database on z/OS®, or a Db2® database on either Linux or Windows.
Some Db2® for z/OS® SQL statements can only be simulated when a Db2® simulation database is used.
There are also some limitations to what you can simulate when you use Db2® as the simulation database because JDBC is used to access both the Db2® and integrated simulation databases.
The following table provides the SQL statements that can be simulated with each simulation database:
| EXEC SQL Command | Considerations when you use Db2® as the simulation database | Considerations when you use the integrated simulation database |
|---|---|---|
| ALLOCATE CURSOR | ||
| ALTER INDEX | ||
| ALTER SEQUENCE | ||
| ALTER TABLE | ||
| ASSOCIATE RESULTSET | ||
| CALL | ||
| CLOSE CURSOR | ||
| CREATE INDEX | ||
| CREATE SEQUENCE | ||
| CREATE TABLE | CHAR columns with length greater than 254 are not supported. | |
| CREATE VIEW | ||
| DECLARE CURSOR | SENSITIVE DYNAMIC cursors are processed as SENSITIVE STATIC cursors. The searched updates and deletes are not detected. | SENSITIVE DYNAMIC cursors are processed as SENSITIVE STATIC cursors. The searched updates and deletes are not detected. |
| DELETE | WHERE CURRENT OF is not supported. | |
| DROP INDEX | ||
| DROP SEQUENCE | ||
| EXECUTE | Not supported. | |
| EXECUTE IMMEDIATE | Not supported. | |
| FETCH | Fetching LOB, XML, and other column types from an insensitive scrollable cursor are not supported. | |
| INSERT | ||
| MERGE | ||
| OPEN CURSOR | ||
| PREPARE | Not supported | |
| SELECT | Use of the DISTINCT keyword in the WHERE clause is not supported. | |
| SET host variable assignment | ||
| UPDATE | WHERE CURRENT OF is not supported. |
You should also consider performance when you choose a simulation database. Because the z/OS Agent uses a network connection to connect to the simulation database, you experience the best performance when you use a database that is located on the same system as the z/OS Agent.