


























          VAX Storage Library System V2.1

          AV-PFA1D-TE
          August, 1991




                           +----------------+
                           |READ THIS FIRST |
                           +----------------+




          Dear VAX SLS Customer:

          Enclosed is your distribution kit for the Version
          2.1 VAX Storage Library System. This version of
          the VAX SLS software incorporates significant
          quality improvements over the V2.0 VAX SLS
          software. Please read the VAX Storage Library
          System Release Notes for a complete description
          of the changes included with this new version.

          Attached to this cover letter is a description of
          two issues we would like to bring to your
          attention. Please read the enclosed descriptions
          carefully to determine if they apply to your
          site.
          Thank you for using the VAX Storage Library
          System.




          Copyright 1991 by Digital Equipment Corporation.
          All rights reserved.  Printed in the U.S.A.
















                                - 2 -



          Problem #1:  A VMS MOUNT restriction may prevent
          VAX SLS software from write-enabling volumes it
          doesn't own


          Problem Description:

          A restriction has been found in the VMS MOUNT
          utility which may prevent the VAX SLS software
          from mounting volumes as write-enabled during a
          system backup. If the VAX SLS software cannot
          mount a volume write-enabled an OPCOM message
          similar to the following will appear:

             %%%%%%%%%%% OPCOM 12-JUL-1991 13:53:44.00 %%%%%%%%%%%
             Message from user SLS on MYNODE
             Volume MTP001 on _MYNODE$MUA0: must be write enabled

          The restriction is due to the way VMS MOUNT
          checks UIC protection for magnetic tape and
          cartridge volumes. Because VAX SLS V2.1 now
          writes volume protection and ownership
          information on volumes used for system backups
          this is a new problem for VAX SLS that did not
          occur with previous versions.
          The circumstances under which this problem occurs
          are as follows:

            1. Multiple standalone nodes or VAXcluster
               systems are performing system backups with
               VAX SLS V2.1.

            2. The VAX SLS software account UICs are not
               uniform among these systems.

            3. Volumes that had been used previously on one
               system or VAXcluster are later used for a
               system backup on a system with a different
               VAX SLS software account UIC.

            4. The protection code written on the volumes
               specifies only READ access for users in the
















                                - 3 -



               WORLD category. Note that the value of the
               PROTECTION symbol defined in the file
               SLS$SYSTEM:SYSBAK.TEMPLATE grants only READ
               access to users in the WORLD category as
               follows:

               $! Reel / Saveset Protection Parameter
               $!
               $ PROTECTION :== S:RW,O:RW,G:R,W:R
               $!

               Therefore, system backup *_SBK.COM files
               that are created from SYSBAK.TEMPLATE may
               show the problem described in this section.



          Problem Background:

          VAX SLS V2.1 software was modified to write a
          protection mask onto the volumes it uses during a
          system backup. The owner UIC of these volumes is
          that of the VAX SLS software account. The value
          of this protection mask is taken from one of the
          following sources:

            1. The PROTECTION symbol in the *_SBK.COM file
               in the SLS$SYSBAK directory, if it is not
               blank.

            2. Otherwise, the default file protection set
               by the SET PROTECTION/DEFAULT command in the
               LOGIN.COM command procedure for the VAX SLS
               software account in the SLS$SYSTEM
               directory.


          The writing of protection and ownership
          information ensures that nonprivileged users
          cannot access VAX SLS system backup volumes
          outside of VAX SLS without either permission from
          the owner of the volume or assistance from a
















                                - 4 -



          privileged user such as the Storage Administrator.

          The restriction with VMS MOUNT is that if a
          magnetic tape or cartridge volume is initialized
          with a protection mask which grants only READ access
          to users in the WORLD category, those users are
          restricted to read- only access regardless of
          process privileges or /OVERRIDE qualifiers on the
          MOUNT command.
          The effect of this restriction is to prevent the
          VAX SLS software from mounting such volumes  as
          write-enabled during a system backup unless the
          VAX SLS software account has a system UIC or a
          UIC identical to that of the OWNER of the volume.

          Note that the problem does NOT appear if users in
          the WORLD category are given both READ and WRITE
          access or if users in the WORLD category are
          given no access at all. In these cases, the VAX
          SLS software will use VOLPRO privilege to mount
          the volume write-enabled even if the owner UIC of
          the volume differs from that of the VAX SLS
          software account. The problem also does not
          affect restore operations.

          Guidelines for Avoiding the Problem:

          The following steps should be taken to ensure
          that VAX SLS software will be able to mount as
          write-enabled all volumes that are used for system
          backups.

            1. Assign all VAX SLS software accounts in your
               network a system UIC.

               A system UIC is one whose group number is
               less than the SYSGEN parameter MAXSYSGROUP.
               VMS MOUNT always grants users in the SYSTEM
               category READ and WRITE access to magnetic
               tape and cartridge volumes, regardless of
               what is specified in a volume's protection
















                                - 5 -



               code. This solution avoids problems with all
               volumes that are initialized with volume
               protection.

            2. IF it is not possible to assign all VAX SLS
               software accounts a system UIC, use the same
               UIC for all VAX SLS software accounts.

               This ensures that the VAX SLS software
               account on each node can write to system
               backup volumes previously written on other
               nodes. Volumes that are owned by users other
               than the VAX SLS software account may have
               to be re-initialized to eliminate the volume
               protection information before they can be
               used for system backups.

            3. If you cannot comply with steps 1 or 2, then
               avoid specifying only READ access for WORLD
               users in your system backup procedures.

               The PROTECTION symbol in your *_SBK.COM
               files and the SET PROTECTION /DEFAULT
               command in the the file SLS$SYSTEM:LOGIN.COM
               define what protection is written onto the
               volume.  Because of the restriction with VMS
               MOUNT, specify either READ and WRITE access
               for WORLD users (W:RW) or no access at all
               for WORLD users.

            4. When users initialize their private volumes,
               they should avoid specifying only READ
               access for WORLD users with the /PROTECTION
               qualifier on BACKUP or INITIALIZE DCL commands
               or with VAX SLS user backups.

               Either specify both READ and WRITE access
               (W:RW), or no access at all for WORLD users.
















                                - 6 -



          Procedure To Modify The VAX SLS Software Account
          UIC:

          The VAX SLS software account is assigned a UIC
          during product installation. If you want to
          change the VAX SLS software account without reinstalling
          the product follow this procedure.



            1.  Shut down VAX SLS software:

               $ @SLS$SYSTEM:SLS$SHUTDOWN

            2. Set default directory to the system
               directory:

               $ SET DEFAULT SYS$SYSTEM
            3. Execute the VMS AUTHORIZE utility to modify
               the SLS account:

               $ MCR AUTHORIZE
               UAF>MODIFY SLS/UIC=[system_uic]

            4. Verify that the SLS identifier was correctly
               modified to reflect the new UIC and exit

               UAF> SHOW/ID SLS
               UAF> EXIT

            5. Modify the UIC ownership of VAX SLS files:

               $ SET FILE/OWNER=[SLS] SLS$ROOT:[...]*.*;*
               $ SET FILE/OWNER=[SLS]
               <device>:[000000]SLS$FILES.DIR

            6. Restart VAX SLS software:

               $ @SYS$STARTUP:SLS$STARTUP
















                                - 7 -



          Problem #2: Problems with Terminating Backups


          General Description:


          A backup that is in progress can be terminated in
          the following ways:

            1. by issuing a STOP/ID command on the backup
               process,

            2. by issuing a STOP/ENTRY command on the
               backup batch job,

            3. by replying "QUIT" to a VAX SLS OPCOM
               request,

            4. by a system crash or process exit.

          In general, terminating a system backup that is
          in progress may affect future system backups in
          two ways:


            1. The volume being written may be left in a
               state that prevents additional data from
               being written to it;

            2. For system backups, the file named in the
               CONTINUE symbol in the *_SBK.COM file for
               the backup job may be left in a state that
               prevents its use.

          Effect of Backup Termination on Volumes:


          When terminated by any method except responding
          "QUIT" to an OPCOM request, the VAX SLS backup
          image cannot write end-of- volume tape marks to
          the end of the volume to which it is writing.
          When this happens, any attempt to write another
          save set to the volume will result in the
















                                - 8 -



          following error:

             %BACKUP-F-CONTINUED, <save-set-name> contains
             a continued file - cannot append

          Previously-written save sets on the volume may be
          read successfully for restore operations.  But
          the volume must be re-initialized with the VMS
          DCL commands INITIALIZE or BACKUP/REWIND before
          new data can be written to it. Therefore, we
          strongly recommend  that VAX SLS users avoid
          using the commands STOP/ID or STOP/ENTRY to terminate
          backup operations that are in progress.

          Effect of Backup Termination on CONTINUE Files:


          VAX SLS software provides the ability for syste
          backup jobs to write multiple save sets
          contiguously onto a single volume set. This
          feature is implemented through the CONTINUE
          symbol in your *_SBK.COM files. If the CONTINUE
          symbol is defined as a file name string, all save
          sets produced by system backups whose CONTINUE
          symbols are the same will write contiguously to a
          single volume or  volume set.

          The volume ID of last volume of the volume set is
          stored in a file whose name is constructed from
          the CONTINUE symbol value in the format:
          SLS$SYSBAK:<continue>.CONT_READY.  While a backup
          is in progress, the file is renamed to
          SLS$SYSBAK:<continue>.CONT_INPROG to prevent
          another backup job from using the same volume
          set.  If a system backup job finds the CONTINUE
          file with the file type .CONT_INPROG, it assumes
          that the volume set is in use by another job and
          proceeds with the backup by allocating and
          initializing a volume in the FREE state.  These
          backup jobs will not update the CONTINUE file to
          allow future system backups to append save sets
          to the volume set used for the backup.
















                                - 9 -



          If you terminate a system backup job, the
          CONTINUE file's name keeps the file type
          .CONT_INPROG, thus preventing other system
          backups from using the CONTINUE file feature to
          store multiple save sets on a single volume or
          volume set.  This results in wasted space on
          large capacity media.



                    Note:  in a future
                    maintenance release of VAX
                    SLS software, the system
                    backup procedure will
                    correctly handle CONTINUE
                    files when the job is
                    terminated by the operator
                    responding "QUIT" or "SKIP"
                    to VAX SLS OPCOM requests.



          Procedure to Handle CONTINUE Files after
          Termination of a System Backup:


          The following is a procedure to recover from
          backup  job termination problems with CONTINUE
          files:

            1. Determine the value of the CONTINUE symbol
               for the system backup which was terminated.

               If the CONTINUE symbol is blank, then no
               further action is required.

               If the CONTINUE symbol has a string value,
               then substitute that string value (without
               the optional /NEW qualifier) for the <continue>
               fields in the following steps.
















                                - 10 -



            2. If the backup was terminated using the
               commands STOP/ID or STOP/ENTRY or by either
               a system crash or program error, use a new
               volume set in future backups.

               It is highly probable that the volume which
               was being written will cause
               %BACKUP-F-CONTINUE errors if you attempt
               again to write to it before it is
               re-initialized.  To cause VAX SLS software
               to start using a new volume set, delete all
               versions of the the CONTINUE file using the
               following command.

               $ DELETE SLS$SYSBAK:<continue>.CONT_INPROG;*

            3. If the backup was terminated by replying
               "QUIT" to the first "REDO, SKIP or QUIT"
               prompt of a system backup job (or by
               replying "SKIP" to all such prompts), then
               you should rename the CONTINUE files.

               Renaming all versions of the CONTINUE file
               to the file type .CONT_READY  allows  VAX
               SLS software to append additional save sets
               to the$ RENAMEor volume set with subsequent
               systemSLS$SYSBAK:<continue>.CONT_INPROG;*  -d:
                     *.CONT_READY;*

               It is not an error if a .CONT_INPROG file
               does not exist.  A new volume set will be
               started with the next execution of a system
               backup with the same CONTINUE symbol value.


            4. If the backup was terminated by replying
               "QUIT" to a load request for the first
               volume then you must delete only the highest
               version of the CONTINUE file using the
               following command.





















               The previous version of the CONTINUE file,
               if any, will contain the correct volume ID
               of the volume to be written:

               $ DELETE SLS$SYSBAK:<continue>.CONT_READY;0

               If there is no previous version of the
               CONTINUE file, then VAX SLS will start a new
               volume set the next time it executes a
               system backup job with the same CONTINUE
               symbol value.
