Alpine pmn CD Player User Manual


 
42 U41117-J-Z125-7-76
Procedures CentricStor - Virtual Tape Library
2.6.3 Scratch mount
To prevent reading in from the physical medium in cases where a logical volume is to be
rewritten anyway, under certain circumstances CentricStor performs a “scratch mount”.
The special features of the scratch mount in CentricStor are as follows:
If the logical volume is migrated, i.e. it is no longer in the TVC, only a “stub” is made
available for the application. This stub contains only the tape headers.
As this stub is always kept in the TVC a scratch mount can always be performed very
quickly as no restore is required from the physical tape.
For the application this means that only access to the tape headers is possible.
If a scratch mount is performed incorrectly this can result in read errors when
an attempt is made to access the other data. In this case the data is not lost:
When a subsequent “normal” mount is performed it is available again.
CentricStor performs a scratch mount under the following conditions, depending on the
frontend (interface of the virtual library):
VAMU The mount command supports a flag which can be used to indicate that the
mount is to be performed as a scratch mount.
VDAS There is a special DAS_MOUNT_SCRATCH command (used only by FSC Networ-
ker). In this case CentricStor performs a scratch mount.
VACS A scratch mount is performed in the following two cases:
“Mount_scratch” with the “pool-ID” parameter without specification of a par-
ticular volume
Mount on a specific volume if this is contained in a pool whose pool ID is not
0
VLMF A scratch mount is performed in the following two cases:
Mount with the “scratch” command with specification of a pool or specific vo-
lume
Mount of a volume that is marked as “scratch”
VJUK No scratch mount is used
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