TAL Reference Manual

Privileged Procedures
TAL Reference Manual—526371-001
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Nonprivileged Procedures
The following PRIV procedure is called by the preceding CALLABLE procedure:
PROC priv_proc PRIV;
BEGIN
!Privileged instructions
END;
Nonprivileged Procedures
A nonprivileged procedure that is called by a CALLABLE or PRIV procedure executes
in privileged mode and can call PRIV procedures.
Privileged Operations
Only procedures that operate in privileged mode can access system global data. Such
procedures can access system data space, call other privileged procedures, and
execute certain privileged instructions. Privileged procedures must be specially
licensed to operate, because they might (if improperly written) adversely affect the
status of the processor in which they are running.
A procedure that operates in privileged mode can use system global pointers and 'SG'
equivalencing:
•
To access system tables and the system data area
•
To initiate certain input-output transfers
•
To move and compare data between the user data area and the system data area
•
To scan data in the system data area
A procedure operating in privileged mode can also:
•
Perform privileged operations through calls to system procedures
•
Execute privileged instructions that can affect other programs or the operating
system
For more information on an extended pointer pointing to a system data, see Appendix
B of the
TAL Programmer’s Guide.
System tables are described in the
System Description Manual for your system.