HLASM Language Reference

Levels of Macro Call Nesting
&SYSNEST
&SYSSEQF
&SYSSTYP
The assembler increments &SYSNEST by one each time it
encounters a nested macro instruction. It retains the incremented
value within the local scope of the macro definition called by the
inner macro instruction. Subsequent nested macro instructions
cause &SYSNEST to be incremented by 1. When the assembler
exits from a nested macro it decreases the value in &SYSNEST by
1.
The assembler assigns &SYSSEQF the character string value of
the identification-field of the outer-most macro instruction statement.
The value of &SYSSEQF remains constant throughout the
expansion of the called macro definition and all macro definitions
called from within the outer macro.
The assembler gives &SYSSTYP the character string value of the
type of the control section in use at the point at which a macro is
called. For a macro definition called by an inner macro call, the
assembler assigns to &SYSSTYP the type of the control section in
effect in the macro definition that contains the inner macro call, at
the time the inner macro is called.
If no control section is generated within a macro definition, the value
assigned to &SYSSTYP does not change. It is the same for the
next level of macro definition called by an inner macro instruction.
Chapter 8. How to Write Macro Instructions 317