On Mon, 28 Nov 2005 14:51:48 +0100, TISLER Zaromil <[EMAIL PROTECTED]
AUSTRIA.COM> wrote:
>Bill,
>
><----- snip ----->
>The existence of signalling
>connectivity created a race condition, in which MVSA and MVSB were
>competing to detect and report the loss of access to the CDS at their
>respective sites. MVSB won the race, detecting and signalling the loss of
>the primary CDS before MVSA detected loss of the alternate. MVSA got
>MVSB's signal, initiated removal of the primary, and then detected the
>inaccessibility of the alternate.
><----- snip ----->
>
>What would happen if MVSA got the race? Would MVSB try to access the
primary
>during acknowledgment of the removal of the alternate CDS? If not, could
it
>survive the loss of connectivity to primary if it (connectivity loss)
would
>be short enough?
Zaromil,
The mirror-image problem would have occurred. MVSA would have
initiated the removal of the alternate, signalling its failure to MVSB.
MVSB would have dutifully begun removing it, and, either in the removal
process or independently at its next heartbeat interval, discovered that
the primary was inaccessible. MVSB would then wait state, leaving MVSA
waiting for a response to its signal.
If the connectivity loss lasts long enough for the I/O subsystem to
reject an access attempt with a permanent I/O error completion code, the
process is irreversible. That must be what happened in Gil's case.
Normal I/O recovery processing would protect the system in the event of a
transient "blip", but if XCF is told that the error is permanent, the CDS
is removed.
Bill Neiman
z/OS Development
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