Alan wrote:
>I think everyone has a good understanding of the issues, Jim.
Based on the previous and subsequent posts to this thread after this
statement , based on Boeblingen's design of the tape390 driver, and based
on the restrictions on the Developer works pages for the tape staring, I
think you assume too much about who understands what or we wouldn't be
having this discussion. ;)
And those that only approach the problem from the a single OS point of view
(Linux or VM/Linux) are missing the point that the shared ESCON tape drives
can be used by multiple OS on multiple LPAR's on multiple CEC's. Or that
the operations staff that have to operate these tape drives may be many
kilometers away for both the CEC's and the users.
Doing a search of the literature from IBM, you might find out that DB2 UDB
is not certified for shared tapes in the backup command because of these
restrictions (probably in some very obscure footnote somewhere). Why?
issue backup to tape on a linux LPAR or EC guest
issue vary online on in an MVS LPAR or attach on for and EC guest on
any LPAR on any CEC that shares the drive
SLES7 - at any time, the backup copy is as good as toast and
the data is available to the other hosts.
SLES8 - after the backup, the backup copy is as good as toast
and the data is available to other hosts.
That does not sound to me as if there is a good understanding of how the
mechanism works!
As long as you use attach under VM (with the default of assign), you can
operate fat dumb and happy. As soon as you specify unassign or you try to
run in LPAR mode, you run into both data integrity and data security
problems big time.
If everyone had a "good understanding" of how ESCON shared tape worked,
then it would have been implemented differently in the first place. Linux
zSeries is still on the low end of the learning curve on this issue.
To answer Tom's question about the extent of the problem:
1 - If you have tape dedicated to the LPAR and no other LPAR can access the
tape you do not have the problem.
2 - running under VM, using attach with the default of assigned, you have
do not have the problem.
3 - running under VM, using attach with unassign, you are exposed to the
problem (the issue that started this thread).
4 - if you are running native or in an LPAR, w/o VM, you are exposed to the
problem.
If you are exposed to the problem, you can have data integrity and data
security problems caused by other EC guests, other LPARS, other CECs, and
other OS who have a path to these tapes.
Regards, Jim
Linux S/390-zSeries Support, SEEL, IBM Silicon Valley Labs
t/l 543-4021, 408-463-4021, [EMAIL PROTECTED]
*** Grace Happens ***
