Environment

Review Function Routines/Function Codes, which describes both the general environment on entry to your function routine and other programming considerations that your function routine should take into account.

If you decide to set up your subsystem to handle command processing calls, make sure that your function routine is in place before you enable the subsystem to handle SSI function code 10. IBM® recommends that you use the IEFSSVT macro to notify MVS™ that your subsystem should be given control whenever Command Processing calls are made. IEFSSVT macro services are available only to dynamic subsystems. Subsystems that are not dynamic can still use the IEFJSVEC service; see Building the SSVT and Enabling Your Subsystem for New Functions for more information.

Do not code a function routine that enters an explicit WAIT or uses a system service that enters a WAIT. Entering a wait can cause degraded system performance.

Data areas commonly referenced are mapped by the following mapping macros. IBM recommends you include them in your function routine:

IEFSSOBH
IEFJSSIB
IEFSSCM
IEZMGCR

The function routine receives control in the following environment:

Environment variable	Value
Minimum authorization	Supervisor state with PSW key 0
Dispatchable unit mode	Task
AMODE	24-bit or 31-bit
Cross memory mode	PASN=HASN=SASN
ASC mode	Primary
Interrupt status	Enabled for I/O and external interrupts
Locks	No locks held
Control parameters	The SSOB, SSIB, and SSCM control blocks reside in storage below 16 megabytes.
Recovery	The function routine should provide an ESTAE-type recovery environment. See z/OS MVS Programming: Authorized Assembler Services Reference EDT-IXG for more information on these macros. Failure to establish a recovery environment ends the processing of the current operator command if an abend occurs. The function routine's recovery should retry. The retry point should take one of the following actions: Ignore the command Indicate to the system the command could not be processed Indicate to the system the command was processed. The system issues error message IEE707E indicating the command failed. Note: Refer to Output Register Information for instructions on what your function routine should specify to the system.

Figure 1 shows the environment on entry to the function routine for SSI function code 10.

Figure 1. Environment on Entry to the Function Routine for SSI Function Code 10