 






          Software
          Product
          Description

          ________________________________________________________________

          PRODUCT NAME:  VAX RMS Journaling, Version 5.4      SPD 27.58.05

          DESCRIPTION

          VAX RMS Journaling helps maintain the data integrity of RMS
          files in the event of a number of failure scenarios. Jour-
          naling helps to protect RMS file data from becoming lost or
          inconsistent.

          VAX RMS Journaling provides the following three methods of
          journaling:

          o  After-image (AI) journaling provides the ability to redo a
             series of modifications to a data file. This type of jour-
             naling helps recover lost or corrupted files. After-image
             recovery restores the contents of the file from the point of
             the latest backup copy of that file.

          o  Before-image (BI) journaling provides the ability to undo a
             series of modifications to a data file. This type of journal-
             ing allows a file to be returned to a previous known state.
             This is useful in the event that a file is updated with erro-
             neous data.

          o  Recovery unit journaling helps maintain transaction in-
             tegrity, where a transaction consists of a group of related
             operations that must be "atomic". That is, either all of the
             operations complete in their entirety or none of the opera-
             tions complete. This type of journaling helps prevent data
             from becoming inconsistent due to the incomplete execution of
             a transaction.


                                       DIGITAL              September 1990

                                                               AE-JG40F-TE

 


          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          Journaling is applied on a file-by-file basis. A file can be
          marked for after-image, before-image, recovery unit journaling,
          or any combination of these methods. Within a given application,
          any combination of journaling methods can be used.

          VAX RMS Journaling stores the information necessary for data
          recovery in files known as journals. Multiple data files may use
          the same journal.

          RMS Recovery Unit Journaling and DECdtm Transactions

          Transactions are defined and managed using the DECdtm transac-
          tion services available in VMS. An RMS recovery unit is a set
          of RMS record operations, performed in the context of a single
          process, that are part of transactions coordinated by DECdtm
          services. RMS recovery units are started automatically by RMS
          and RMS recovery units are committed or aborted along with the
          transaction of which they are a part.

          VAX RMS Journaling functions as a participating resource manager
          through the utilization of DECdtm services. DECdtm services
          are implemented using a two phase commit protocol as described
          in the VMS Operating System Software Product Description (SPD
          25.01.xx). Recovery unit journaling supports both a one-phase
          and a two-phase commit protocol.

          Remote RMS files (files accessed by means of the DAP/FAL proto-
          col) that are marked for recovery unit journaling can be modi-
          fied within a transaction, and will be included in the "atomic
          unit of work" defined by the transaction. Also, the modifica-
          tions made to RMS files marked for recovery unit journaling
          can be combined with modifications made using any resource
          manager that supports DECdtm services into a single "atomic"
          transaction.

          The Recovery Unit Facility (RUF) services have been superseded
          by DECdtm services. However, the RUF services are still sup-
          ported and are transparently emulated using the DECdtm services.
          Existing applications written using the RUF services continue to
          work without recompilation or relinking.

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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          Supported File Organizations

          All RMS file organizations are supported by VAX RMS Journaling.
          Any sequential, relative, or Prolog 3 indexed file can use
          journaling. However, the following restrictions apply:


































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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          o  Prolog 1 and Prolog 2 indexed files are not supported by VAX
             RMS Journaling.

          o  Sequential files are limited to a record size of 32667 bytes.

          o  Files marked for recovery unit journaling cannot be written
             with the DCL WRITE command.

          o  Stream files cannot be modified in shared mode in a recovery
             unit.

          o  Sequential files having VFC record format do not allow shared
             access for recovery unit journaling.

          When using recovery unit journaling with shared fixed-length
          sequential files, any abort processing overwrites records added
          to the recovery unit with zero bytes (null characters). This
          occurs because the record cannot be deleted from the file.

          All files that are marked for journaling must reside on Files-
          11 Structure Level 2 disks. All journals must also reside on
          a Files-11 Structure Level 2 disks. It is recommended that
          journals used for after-image journaling reside on a disk volume
          that is different from the disk volume where the data file that
          uses the journal resides. Journaling across a network or to a
          tape device is not supported.

          Marking Files for Journaling

          VAX RMS Journaling is enabled on a file-by-file basis. Files
          marked for after-image, before-image, and recovery unit journal-
          ing are enabled by using qualifiers to the DCL command SET FILE.
          Any combination of qualifiers may be used with a particular SET
          FILE command or series of SET FILE commands. Files are unmarked
          for journaling using the SET NOFILE command.

          The most recent SET FILE command for a given file overrides all
          previous SET FILE commands for that file.

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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          Successful marking of an RMS file for journaling requires ex-
          clusive access to the file specified in the SET FILE command.
          Exclusive access means the RMS file being marked for journal-
          ing must be closed; that is, application programs accessing
          that file must be shut down before the file can be successfully
          marked for journaling.

          No modifications to application programs are required for long-
          term (after-image or before-image) journaling. Once a file has
          been marked for long-term journaling, journal information will
          be written to the journal each time the file is modified. The
          file must have been opened subsequent to the issuance of the SET
          FILE command that marked the file for VAX RMS Journaling. All
          modifications to the file are recorded in the journal until the
          file is unmarked for journaling.

          Modifications to application programs are required for recovery
          unit journaling. At a minimum, the program must specify the
          start and end of a recovery unit, using the recovery unit system
          services. When a file is marked for recovery unit journaling,
          all modifications to that file within an application must be
          within a recovery unit.

          Journal File Maintenance

          After-image and before-image journals require periodic main-
          tenance. Because journal files can expand indefinitely and a
          journal must reside on a single volume set, occasional remarking
          of a file for journaling and all of the associated operations
          is required. This implies that applications accessing RMS data
          files marked for after-image or before-image, or both, jour-
          naling must be stopped periodically for journal maintenance
          operations.

          Recovering Data - Long-Term Journaling




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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          In the case of long-term (either after-image or before-image)
          journaling, data recovery is done using the RMS Recovery Util-
          ity. Recovery is on a file-by-file basis and must be explicitly
          requested; it is not done automatically. The RMS Recovery Util-
          ity is invoked at DCL level to either roll forward or roll back
          changes to the file. The Recovery Utility requires exclusive ac-
          cess to the file being recovered. Changes may be rolled forward
          or rolled backward until a time specified by the user.

          To roll forward a file and redo changes, a VMS backup copy of
          the file must be on disk. This backup copy must have been made
          after the file was marked for after-image journaling.

          Recovering Data - Recovery Unit Journaling

          No user intervention is required to roll back a recovery unit
          that is incomplete. The rollback of an incomplete transaction
          is started and completed automatically the next time the user
          accesses the file.

          Interaction with Backup

          To recover data using after-image journaling, a backup copy
          of the file must be available. This copy must be made with
          the Backup Utility (BACKUP); a copy of the file made with the
          COPY or CONVERT command cannot be used. A backup copy of the
          file must be made after the the SET FILE/AI_JOURNAL command
          is issued but before the file is opened for update. BACKUP
          requires exclusive access to files being backed up. No user
          or application program may access the file until BACKUP is
          finished.








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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          The use of BACKUP/RECORD is recommended. If the file is then
          rolled forward, the modifications that have been made since the
          most recent backup are applied.

          If a backup copy of a file is rolled forward with the RMS Recov-
          ery Utility, you must remark the file for after-image journaling
          with the SET FILE/AI_JOURNAL command. A backup copy of that file
          must be made after it has been marked for after-image journaling
          and before application updates are allowed.

          A backup copy of the file must be remarked for journaling if it
          is to be used in place of the original file.

          Interaction with VAX Volume Shadowing

          VAX Volume Shadowing may be used in conjunction with after-image
          journaling. After-image journaling helps recover data in the
          following cases not addressed by VAX Volume Shadowing:

          o  Mistaken deletion of a file by a system user or operator

          o  Corruption of the file system pointers

          o  RMS file corruption due to a software error or incomplete
             bucket write operations to to an indexed file

          Failures Not Addressed by RMS Recovery Unit Journaling

          Recovery unit journaling alone does not provide recovery in
          cases when a multi-block bucket write operation to an indexed
          file is in progress, leaving the bucket in the indexed file in
          a corrupt state. Use after-image journaling in conjunction with
          recovery-unit journaling to recover from the following failed
          multi-block bucket write operations:

          o  Failure of the VAX host during a multi-block write operation,
             such as a VMS crash, halt, power failure, or system shutdown.

          o  Permanent loss of path to the disk during a multi-block write
             operation.

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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          o  Cancellation of a multi-block write operation in progress.
             This occurs only in disks using DUDRIVER. Other disk drivers
             ignore the cancellation of I/O and are not affected.

          HARDWARE REQUIREMENTS

          Refer to the VMS Operating System Software Product Descrip-
          tion (SPD 25.01.xx) for hardware requirements and supported
          processors.

          OPTIONAL HARDWARE

          None

          CLUSTER ENVIRONMENT

          This layered product is fully supported without restrictions
          when installed on any valid and licensed VAXcluster* configura-
          tion. The HARDWARE REQUIREMENTS sections of this product's Soft-
          ware Product Description and the VMS Operating System Software
          Product Description (SPD 25.01.xx) list any special hardware
          required by this product.

          *  VAXcluster configurations are fully described in the VAXclus-
             ter Software Product Description (SPD 29.78.xx) and include
             CI, Ethernet, and Mixed Interconnect configurations.

          SOFTWARE REQUIREMENTS

          VMS Operating System

          VMS Tailoring

          For VMS V5.x, the following VMS classes are required for full
          functionality of this system integrated product:

          o  VMS Required Saveset

          For more information about VMS classes and tailoring, refer
          to the VMS Operating System Software Product Description (SPD
          25.01.xx).

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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          OPTIONAL SOFTWARE

          None

          GROWTH CONSIDERATIONS

          The minimum hardware/software requirements for any future ver-
          sion of this product may be different from the requirements for
          the current version.

          ORDERING INFORMATION

          Software Licenses: QL-VDVA*-**
          Software Documentation: QA-VDVAA-GZ
          Software Product Services: QT-VDVA*-**

          *  Denotes variant fields. For additional information on avail-
             able licenses, services and media, refer to the appropriate
             price book.

          The above information is valid at the time of release. Please
          contact your local Digital office for the most up-to-date infor-
          mation.

          SOFTWARE LICENSING

          This software is furnished under the licensing provisions of
          Digital's Equipment Corporation's Standard Terms and Condi-
          tions. For more information about Digital's licensing terms and
          policies, contact your local Digital office.









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          VAX RMS Journaling, Version 5.4                     SPD 27.58.05



          LICENSE MANAGEMENT FACILITY

          This system integrated product supports the VMS License Manage-
          ment Facility.

          License units for this product are allocated on a CPU-capacity
          basis.

          For more information about the License Management Facility,
          refer to the VMS Operating System Software Product Description
          (SPD 25.01.xx) or the License Management Utility Manual of the
          VMS documentation set.

          For more information about Digital's licensing terms and poli-
          cies, contact your local Digital office.

          SOFTWARE PRODUCT SERVICES

          A variety of service options are available from Digital. For
          more information, contact your local Digital office.

          SOFTWARE WARRANTY

          Warranty for this software product is provided by Digital with
          the purchase of a license for the product as defined in the
          Software Warranty Addendum of this SPD.

          [TM] The DIGITAL Logo, DECdtm, VAX, VAX RMS and VMS are trade-
               marks of Digital Equipment Corporation.










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