ADSM-L

Flash from Wash Sys Center regarding TSM and LABEL LIBVOL

2000-05-24 13:11:07
Subject: Flash from Wash Sys Center regarding TSM and LABEL LIBVOL
From: Mike Hedden <Mike_Hedden AT FPL DOT COM>
Date: Wed, 24 May 2000 13:11:07 -0400
Title: Potential Problem with ADSM and Tivoli Storage Manager when using
LABEL LIBVOL command

Organization:  WSC
Product: Tivoli Storage Manager Release: All Releases
Document Number: Flash10029 Last Revised: 05/22/2000

This San Jose Systems Center flash is intended to describe a potential
problem with ADSM and Tivoli Storage Manager when using the LABEL LIBVOL
command.

Problem Description:
In certain limited circumstances, the Adstar Distributed Storage Manager
(ADSM) and the Tivoli Storage Manger (TSM) servers for the AIX, HP, SUN,
and Windows platforms can overwrite the label of an existing in-use server
volume with the LABEL LIBVOL command when the OVERWRITE=YES parameter is
specified. If a label is overwritten for a volume in-use by a specific ADSM
or TSM server, the data on that volume is no longer accessible because the
operation of writing a new label to the volume causes a file mark to be
written to the tape volume after the label. This file mark causes any data
after the file mark to not be accessible. We are committed to resolve this
situation and provide a corrected version of the server. An announcement
will be made once corrected versions of the servers are available. This
problem is documented in server apar IC26881. Until servers are available
with this fix, the "OVERWRITE=YES" parameter on the "LABEL LIBVOL" command
should not be used.

Please note that specific circumstances must be encountered in order to be
susceptible to this problem. If your ADSM or TSM server is administered in
the following manner, you may not be impacted or susceptible to this
problem:

If the "LABEL LIBVOL" command is not specified with the "OVERWRITE=YES"
(the default value for this parameter is OVERWRITE=NO) parameter.

If the actual library contents are never altered manually. In particular,
volumes are only entered or removed from the library using the library I/O
station.

If volumes are ONLY inserted or removed from your library using the
"CHECKIN LIBVOL" and "CHECKOUT LIBVOL" commands.

The possibility of encountering this error is unlikely if care is given in
maintaining the actual library inventory and the appropriate server
commands are used to manipulate volumes within a library.

When was this Problem Introduced?

The problem was introduced in the following server levels:

For the ADSM V312 server, the error was introduced in the 3.1.2.50 server
level for libraries of type "SCSI".

For the TSM V370 server, the error was introduced in the 3.7.0.0 server
level for libraries of type "SCSI".

For the TSM V370 server, the error was introduced in the 3.7.3.0 server
level for libraries of either type "349X" or type "ACSLS".


Do I have This Problem?

The situations which can cause this error vary depending on the type of
library defined to the server. To determine the type of library defined to
the ADSM or TSM server, issue the command QUERY LIBRARY and evaluate the
"Library Type" field. The library types affected and related situations
are:

If the library type is "SCSI", a label can be overwritten only when the
logical library inventory known by the server is not synchronized with the
actual library when the LABEL LIBVOL SEARCH=YES OVERWRITE=YES command
executes. If the logical library inventory tracked by the server is not
synchronized with what is in the library and the server command LABEL
LIBVOL SEARCH=YES OVERWRITE=YES is issued, the server will search each slot
in the library and if a volume is encountered that the server does not know
about based on the information it is tracking, the server may attempt to
overwrite the volume label. The server will ONLY attempt to overwrite the
label if the LABELSOURCE=PROMPT option is also specified on the command or
if the external label for the volume has been changed such that the
external label no longer matches the label previously written to the tape
volume.


One example of how this could occur is that a number of tape volumes were
removed from the library using the CHECKOUT LIBVOL command. A number of new
tapes were inserted into the library but one of the volumes previously
checked out of the library was inadvertently included in the set of volumes
that were inserted. When the LABEL LIBVOL command was subsequently issued,
the new volumes were handled correctly but the previously used TSM or ADSM
volume was inadvertently re-labeled.

If the library type is of type "349X" or "ACSLS", a label can be
overwritten only when the logical library inventory known by the server is
not synchronized with the actual library when the LABEL LIBVOL SEARCH=YES
OVERWRITE=YES command executes. If the logical library inventory tracked by
the server is not synchronized with what is in the library and the server
command LABEL LIBVOL SEARCH=YES OVERWRITE=YES is issued, the server will
search each slot in the library and if a volume is encountered that the
server does not know about based on the information it is tracking, the
server may attempt to overwrite the volume label. The server will ONLY
attempt to overwrite the label if the external label for the volume has
been changed such that the external label no longer matches the label
previously written to the tape volume. In order for the possibility of a
"349X" or "ACSLS library volume to have the label for an in-use volume
overwritten, the volume must have been checked out of the library using the
CHECKOUT L
IBVOL command, the external label needs to have been changed, the volume
had to be placed back in the library without using the I/O station for the
library, and the volume was not checked in to the library using the CHECKIN
LIBVOL command.



Workaround:

Patch for IP26881 (label libvol pblm) - AIX server is available on the
internet
For ADSM version 3.1.2, Patch can be found in the directory
storage/adsm/fixtest/v3r1/aixsrv/3.1.2.57. "get" the file PA31257.bff and
apply it via SMIT.
For Tivoli Storage Manager version 3.7, Patch can be found in the directory
storage/tivoli-storage-management/patches/server/AIX/3.7.3.1. "get" the
file PA3731.bff and apply it via SMIT.

For those platforms and levels without patches and a volume is suspected of
having it's volume label overwritten, please see the detailed description
of the problem and trace recommendations in apar IC26881. Please also
consider performing an AUDIT VOLUME FIX=NO for the volume in question. If
the results from the audit volume indicate that the data is indeed not
usable from that volume, the following are the recommendations for
recovery:


If the volume is assigned to a primary storage pool and the primary storage
pool has been backed up to a copy storage pool:

Update the volume status to destroyed for the affected volume using the
"UPDATE VOLUME <volName> STATUS=DESTROYED".

Use either the "RESTORE VOLUME <volName>" or the "RESTORE STGPOOL" commands
as documented in the Administrators' Reference to recover the data from the
copy storage pool to the primary storage pool.

If the volume is assigned to a primary storage pool and the primary storage
pool has NOT been backed up to a copy storage pool:

Update the volume status to destroyed for the affected volume using the
"UPDATE VOLUME <volName> STATUS=DESTROYED".

Use the command "QUERY CONTENTS <volName>" to identify what was on the
volume.

After determining the data on the volume, have the affected clients re-send
the data.

If the volume is assigned to a copy storage pool:

Update the volume status to destroyed for the affected volume using the
"UPDATE VOLUME <volName> STATUS=DESTROYED".

Issue the command "BACKUP STGPOOL <srcPool> <targetPool>" where the
<srcPool> is the name of the primary storage pool where the data resides
and the <targetPool> is the name of the copy storage pool destination. This
will copy the data back to the copy storage pool.

If the volume was used for a server external data operation such as
database backup or export:

For export volumes, perform the export operation again that was used to
create the volume.

For database backup volumes, perform a "FULL" database backup using the
"BACKUP DB TYPE=FULL" command. This establishes a current database backup.

Conclusion:

Until servers are available with this fix, the "OVERWRITE=YES" parameter on
the "LABEL LIBVOL" command should not be used. Also, administer the server
and the tape library so that the information the server tracks about the
volumes and their locations in the library is synchronized with what is
actually in the library. Specifically, any operation to insert or remove a
tape volume into or out of the library should be done using the "CHECKIN
LIBVOL" and the "CHECKOUT LIBVOL" commands respectively. In the event that
some action has occurred to either the server or the library such that this
information is no longer synchronized, an "AUDIT LIBRARY" command should be
done on the server so as to validate and correct the information the server
has about the library and it's contents.





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