Hi,

IMO, the first save area should always be below the line.
It is provided by the operating system so that the main program of the
called application (EXEC PGM=...) can store the registers on call there.
And the first program may be AMODE 24 :-)

On the other hand, I would never use TCBFSA to do anything with it.
Because, for example, you would try to walk the save area chain from there,
you are stuck, because the forward pointers are not set correctly by LE and others. What you should do instead: fetch register 13 and walk back, by using the backward pointers, which are much more reliable in the general case. When doing this, you could check for the value in TCBFSA to see, if you arrived at the first save
area. But you could also check for NULL in the backward pointer.

HTH, kind regards

Bernd


Am 13.02.2018 um 10:07 schrieb Steff Gladstone:
Hi,

I am in the process of converting several routines to AMODE=31 RMODE=ANY.
One of them references the address of the first problem program save area
found in the TCB.

The field is defined as follows:

TCBFSA   DS    0A -    ADDRESS OF THE FIRST PROBLEM PROGRAM SAVE AREA

                 DS    FL1 -   FIRST BYTE OF TCBFSA
@G381P9A

TCBFSAB  DS    AL3 -   ADDRESS OF THE FIRST PROBLEM PROGRAM SAVE AREA

My question:  what is the status of the first byte?  It does not seem to
contain flag bits as is often the case.  On the other hand, defining the
field TCBFSAB seems to imply that the address is a 24-bit address.  So in
AMODE=31 can the first problem program save area (which is provided by the
system to the top-level program) be above the line?  Should I relate to all
four bytes as the address of the FSA?  Or could the first byte contain
garbage?

Thanks,
Steff

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