The application server runs in 31-bit addressing mode (AMODE 31). In single user mode, the database manager transfers control to the application in the addressing mode established during link editing of the program. The database manager continues to operate in 31-bit addressing mode when control returns from the application program.
If you are writing a multiple user mode application, your application is not affected by the addressing mode of the application server.
Refer to the DB2 Server for VSE System Administration manual for information on single user mode and user exits.