Query Bands and External Routines
External routines can access the query band information for both sessions and transactions. External routine is the generic term to describe external procedures, UDFs, and user‑defined methods.
For example, SQL procedures can make SQL requests to set the query band of the transaction using a SET QUERY_BAND request. An SQL procedure can also retrieve the current query band using the QUERY_BAND built-in function.
An external procedure can set the transaction query band by calling an SQL procedure. You can also use an FNC call to retrieve the query band or to get the value of a name within it.
Note that there is no FNC interface to set a query band (see SQL External Routine Programming for details).