I'm sorry to rise to the bait, but the nearly universal misunderstanding of the
MAKEBUF command is one of my sore spots.
<PEDANT>
There is absolutely nothing about MAKEBUF that provides any sort of separation
of the records in the program stack. Successive reads from the stack will
completely ignore any MAKEBUF point and happily continue to read records until
the stack is empty, with no indication that a MAKEBUF point was passed.
To ensure that no more records are read from the program stack than were placed
there after a MAKEBUF, it is necessary to do a Rexx Queued() or SENTRIES command
at the MAKEBUF point to determine how many records are already on the stack, and
then remove no more than were added after the MAKEBUF. This essentially renders
the MAKEBUF/DROPBUF superfluous.
The ONLY thing that MAKEBUF does is to reset the FIFO pointer to equal the LIFO
pointer. This is quite handy because it allows one to place a group of records
on the top of the stack in FIFO order. Without MAKEBUF, this operation would
require reading all the records off the stack, stacking the new records FIFO,
then restacking FIFO the original records.
The closest that MAKEBUF comes to a "separate what you place in the stack from
what is already there" operation, is that if all of the records that were added
to the program stack after a MAKEBUF command are not removed, the remaining
records can be deleted with the appropriate DROPBUF.
</PEDANT>
If at some point, CMS is given the benefit of multiple program stacks (as in the
TSO/REXX environment) you could truly "separate what you place in the stack from
what is already there" by placing the new records in a new stack. At that
point, MAKEBUF and DROPBUF will become vestigial. TSO/REXX's NEWSTACK/DELSTACK
commands and the ability to create "a stack of stacks" is what everyone seems to
think MAKEBUF/DROPBUF provides.
-Chip-
On 9/15/09 15:49 Kris Buelens said:
Yes, DROPBUF 0 would be even better, a MAKEBUF is not required in such a
server I'd say: you'd use it to separate what you place in the stack
from what is there already, but as you code DROPBUF 0, there is surely
nothing anymore to separate your stuff from.
