Calling conventions of the Classic Interface

The Classic Interface uses a single control block $UCHECK to pass information to the exit routine. The exit routine uses $UCHECK to pass information back to the Classic Interface.

The $UCHECK control block is mapped by the $UCHECK macro. The macro is defined in member KOBGMAC of &thilev.TKANMAC.

The Classic Interface maintains the control block for the entire duration of the session.

Restriction: The $UCHECK work area for the configuration is limited to 512 bytes. If your installation requires a larger work area, perform these steps:

  1. Perform a GETMAIN for the additional storage required.
  2. Place the pointer to this GETMAIN area in $UCHECK.
Note: Do not try to enlarge the work area in another way because this causes an overlay of essential control blocks for the Classic Interface. Results are then unpredictable.

If you modify the RACF® RACROUTE macro, you must perform a GETMAIN for at least 512 bytes for use as the WORKA parameter.

The Classic Interface calls the user exit module with these conventions:
Register 1
Address of parameter list
Register 13
Address of a standard save area
Register 14
Return address
Register 15
Entry point address (in)
Register 15
Return code (out)
Word 1
Address of control block