This variable indicates the catalog name to be used when Database Connectors searches for objects in the database. Note that not all data sources support a catalog. Using A_DB2_CATALOG with other variables, such as USER_PATH and A_DB2_TABLE_TYPES, can speed up the finding of tables in large databases. It can also prevent an error 9/14: More than one table with the same name, thereby enabling access to tables with identical names, but with different catalogs.
For example, If USER_PATH and A_DB2_CATALOG are used, the form of the SQL statement is modified from:
select COL1, ... from TABLENAME ...
to:
SELECT COL1, ... FROM [catalog.][username.]TABLENAME ...
where catalog and username are filled in if provided.