 






     Software
     Product
     Description

     ________________________________________________________________

     PRODUCT NAME:  VAX Data Distributor, Version 2.2    SPD 27.76.05

     DESCRIPTION

     VAX Data Distributor manages the distribution of relational
     data. Operations called transfers define what data and data
     definitions are to be moved (the source) and where they are to
     be moved to (the target). The target need not be on the same
     system as the source.

     Distributing data in this way has several benefits, particularly
     when the target is on a different system from the source:

     o  Users can query a database local to them rather than having
        to access a remote database. This provides faster and more
        regular access.

     o  Congestion on the source database is reduced as a result of
        the use of the target.

     Methods of Data Distribution

     There are three transfer types: extraction, extraction rollup,
     and replication. For each type of transfer, the source can be
     all the table definitions and data within the source database or
     databases, or a subset of those definitions and data.

     Extraction

     The source database can be a VAX Rdb/VMS database, or one from
     another database management system, such as DB2 (tm), accessed
     using one of Digital's interoperability products, such as VIDA
     for DB2[TM].

                                  DIGITAL               November 1990

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     The target can be a VAX Rdb/VMS database, or a set of tables
     created by VAX Data Distributor in an existing VAX Rdb/VMS
     database. If it is a database, a new version is created every
     time the transfer executes. If it is a set of tables, the data
     in the tables are deleted and new data, from the source, are
     inserted every time the transfer executes.

     Users can update the target. However, their updates are not
     reflected in the new version of the target created when the
     transfer next executes. Extraction Rollup

     The same range of source databases is available for extraction
     rollup as for extraction. However, an extraction rollup has
     more than one source database. The source databases can be
     of different types, for example, one VAX Rdb/VMS and one DB2
     database.

     The target must be a VAX Rdb/VMS database. A new version is
     created every time the transfer executes. As for extractions, it
     can be updated by users, but updates will not be reflected in
     the new database created when the transfer next executes.

     Replication

     The source database must be a VAX Rdb/VMS database.

     The target can be a VAX Rdb/VMS database, or a set of tables
     created by VAX Data Distributor in an existing VAX Rdb/VMS
     database. The target is created when the transfer first executes
     (is initialized). Subsequent executions of the transfer apply
     the updates that have been applied to the source since the last
     transfer to the target.

     Hence, the difference between replication and the other two
     styles of transfer is that replication makes the data at the
     target identical to that at the source by updating it rather
     than rebuilding it. However, if necessary, the transfer can be
     reinitialized and, in this case, the target is rebuilt.

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     Users must not update the target. However, if the target is a
     set of tables within an existing database, other tables in the
     database can be updated (unless they are the target of other
     replication transfers).

     Other Features

     Schedules

     For every transfer, a schedule can be defined, specifying when
     the transfer is to execute. The transfer can also be executed by
     the transfer definer at a time when it is not scheduled.



























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     Pre- and Post-Transfer Command Procedures

     A transfer can have associated with it DCL command procedures
     that execute before and/or after a transfer executes. Potential
     uses of such procedures include:

     o  Making the network between the source and target systems
        available.

     o  Notifying users by VAXmail that the transfer has completed
        and reporting on the status with which it did so.

     o  Creating indexes on tables in the target database.

     Multiple Transfers

     A database can be the source for more than one transfer. For
     example, a VAX Rdb/VMS database could be the source for a repli-
     cation of some tables, an extraction of some columns from other
     tables, and also one of the source databases for an extraction
     rollup including yet another subset of the data.

     Since the target of an extraction or replication can be a set
     of tables in an existing database, such a database can be the
     target of more than one transfer. However, it cannot be the
     target of an extraction rollup, and no table within the database
     can be the target of more than one transfer.

     A database can be both a source and a target database. For
     example, a database may be the target of a replication transfer,
     and may also be the source of other replications.

     Centralized Storage of VAX Data Distributor Information

     Transfer and schedule definitions and the status of every trans-
     fer are consolidated in a VAX Rdb/VMS database known as the
     transfer database. This database services a VAX or a VAXcluster.

     Syntax

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     The interactive SQL and RDO utilities of VAX Rdb/VMS include VAX
     Data Distributor statements, such as:

     o  CREATE TRANSFER, in which the source and target are spec-
        ified. Specification of the source includes selecting the
        tables, and the rows and columns of those tables, to be
        transferred.

     o  CREATE SCHEDULE, in which the frequency of execution is
        specified.

     o  SHOW TRANSFER, which displays the definition of the transfer
        and that of the associated schedule if there is one, and the
        status of the transfer, including the date and time at which
        it last executed.

     Security

     To create a transfer, it is necessary to have SELECT access to
     the source database and to the tables transferred. To create a
     replication, it is also necessary to have CREATETAB privilege on
     the source database.

     If the target database is created by VAX Data Distributor, it
     is created with the VAX Rdb/VMS default protection. If it is
     necessary to be more restrictive for an extraction or repli-
     cation, the database can be created in advance and the target
     specified as tables within it. Tables are always created with
     the VAX Rdb/VMS default protection. This can be altered in a
     post-transfer DCL command procedure.

     The data in the transfer database are protected from direct
     access by users lacking the required privileges.

     Relationships with Other Products

     VAX Data Distributor requires VAX Rdb/VMS. It can be used with
     any one of the three VAX Rdb/VMS packaging options. Sites need-
     ing to tailor targets (for example, creating indexes) must use
     either the interactive SQL utility or the RDO utility, both of

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     which are supplied with the Interactive and Full Development
     options of VAX Rdb/VMS.

     Since these utilities can perform operations on remote as well
     as local databases, the operations can be performed from another
     node on the network provided the VAX Rdb/VMS Run-Time Only
     option is installed in the target VAX.

     If CDD/Plus is present on the target system, data definitions
     from target databases can be placed in the dictionary by using
     the INTEGRATE statement of the VAX Rdb/VMS SQL or RDO utility.

     In addition to VAX Rdb/VMS, source databases for extractions
     and extraction rollups can be databases accessed via VIDA for
     DB2[TM] or DEC RdbAccess for ORACLE[R] on VMS.

     Where to Install VAX Data Distributor

     It is not necessary to install VAX Data Distributor on every
     system involved in a transfer. It must be installed:

     o  On the source system of a replication.

     o  On either the source or the target system, or both, of an
        extraction or extraction rollup.














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     Limitations

     The syntax to specify as the target, not a new database, but
     a set of tables within an existing database, is available in
     interactive SQL but not in RDO. Since interactive SQL is not
     provided with the Run-Time Only option of VAX Rdb/VMS, use of
     this feature requires either the Interactive or Full Development
     option of VAX Rdb/VMS.

     Record selection, conditional and value expressions available
     in a transfer definition are a subset of those supported by the
     source database management system.

     Indexes, constraints, triggers, collating sequences and ACLs are
     not copied to target databases.

     VAX Data Distributor does not provide commit-time replication
     of changes. That is, updates to the source are transferred to
     the target when a replication transfer executes, not whenever an
     update transaction is committed on the source database.

     HARDWARE REQUIREMENTS

     VAX, MicroVAX, VAXstation, or VAXserver configuration as speci-
     fied in the System Support Addendum (SSA 27.76.05-x).

     SOFTWARE REQUIREMENTS*

     VAX Rdb/VMS (any of the three options)

     For Systems Using Terminals (No DECwindows Interface):

     VMS Operating System

     For Workstations Running VWS:

     VMS Operating System
     VMS Workstation Software

     *  Refer to the System Support Addendum (SSA 27.76.05-x) for
        availability and versions of required software and for infor-
        mation regarding components of VMS DECwindows.

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     ORDERING INFORMATION

     Software Licenses: QL-VDRA*-**
     Software Media: QA-VDRA*-**
     Software Documentation: QA-VDRAA-GZ
     Software Product Services: QT-VDRA*-**

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

     SOFTWARE LICENSING

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

     LICENSE MANAGEMENT FACILITY SUPPORT

     This layered product supports the VMS License Management Facil-
     ity.

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

     For more information on the License Management Facility, refer
     to the VMS Operating System Software Product Description (SPD
     25.01.xx) or the License Management Facility manual of the VMS
     Operating System 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

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     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]  DB2 is a trademark of IBM Corporation.

     [R]   ORACLE is a registered trademark of Oracle Corporation.

     [TM]  The DIGITAL Logo, VAX, VMS, MicroVAX, VAXstation and
           VAXserver are trademarks of Digital Equipment Corporation.





























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