Tom Cluster wrote:
Hello, VM experts,
I'm preparing myself for teaching the mysteries of VSE and VM systems
work and I'm reminded that when one prepares to teach something one
discovers many holes and uncertainties in one's own knowledge. Today
I thought I'd educate myself about IPL bootstrap records in case one
of my students asks about them. My theory, which I wanted to test,
was that they're written by ICKDSF whenever an INIT is done (for MVS
and VSE volumes) or a CPVOL FORMAT is done (for VM volumes). Based on
what I've seen today, this seems to be true.
But while looking around our system I discovered a volume that had
originally been created for VSE use as a full-pack minidisk. In other
words, it had been prepared using ICKDSF INIT (which would have
created a vtoc). However, somewhere along the way it was decided that
this volume would have several minidisks on it. In other words, it
was no longer to be a full-pack minidisk. CPVOL FORMAT was never used
on this volume, so cylinder 0 was left unchanged, with no allocation
information. (If it were to have allocation information, it would
have been PERM for the whole volume.) My initial reaction was
surprise, but then I figured that possibly CP can tolerate a volume
without allocation information as long as its sole use is PERM. It
sure seems to be true that such a volume needs only a VOL1 label to
make CP happy.
My question is this: is there any reason to be concerned about such a
volume not having an allocation map?
- Tom
P.S. The IPL bootstrap records are different between VSE and VM, but
since we're not IPLing using this volume, that isn't an issue.
Tom Cluster
County of Sonoma
Santa Rosa, CA
(707) 565-3384 (Tuesdays and Wednesdays only)
Do not be concerned. The CP Owned volumes are the only ones that need
the allocation map. As for the ipl bootstrap records, they are written
by the SALIPL process for VM. It has been too many years for me to
remember how they are written on the MVS based systems. Even if I
remembered, it would probably still on it be current. Suffice it to say
that they are written only on volumes that are explicitly intended to be
IPL volumes, not on every volume.
As long as a volume has been initialized with a volser that CP can read,
the volume can be attached to SYSTEM and have minidisks on it. When a
volume is changed from being OS or VSE format to one housing minidisks,
it is probably advisable to format cylinder 0 with CPFMTXA (ICKDSF
under the covers) to insure that it is not usable by that other
platform as that could lead to data integrity problems if a dataset were
to be allocated and written on the volume by mistake. While formatting
cyl. 0, change the volume serial, also, as an extra measure of caution..
