HP 3000 Manuals

ALLBASE/Replicate User's Guide

Chapter 1  Introduction to ALLBASE/Replicate 

Overview of ALLBASE/Replicate 

ALLBASE/Replicate allows you to take committed transactions on a source
DBEnvironment, move them over an existing network, and duplicate them[REV
BEG] on a target DBEnvironment.  When committed transactions for tables
on the source are duplicated on the target, the source is being
replicated.[REV END]

The source is called the master DBEnvironment, or the primary 
DBEnvironment, while the target is usually referred to as the slave 
DBEnvironment, or the secondary DBEnvironment.
[REV BEG]

The slave DBEnvironment is usually on a different machine than the
master.  However, you may place the master and slave DBEnvironments in
different locations on the same machine.

The purpose of replication is to ensure that the tables that are on the
slave are a near-real-time, exact copy (mirror image) of the tables on
the master.[REV END]

You can divide the set of tables in the master DBEnvironment into subsets
called partitions.  You can control which tables are replicated by
specifying which partitions on the master will be replicated.  A
partition may include every table in the master DBEnvironment, or just a
subset of the DBEnvironment containing one or more tables.  A table may
be associated with only one partition.  Partitions are discussed further
in chapter 2, "Basic Concepts of ALLBASE/Replicate."

The transfer and duplication activities that bring about replication are
together referred to as resynchronization.  There are two kinds of
resynchronization:  soft resynchronization and hard resynchronization.

Soft resynchronization is the process carried out by the
ALLBASE/Replicate applications supplied with the product, which run on
the master and the slave.  The application that runs on the master is
called REPMAST, while the application that runs on the slave is called
REPSLAVE. Soft resynchronization continuously transfers and applies
committed transactions from the master to the slave in a normal
ALLBASE/Replicate environment.

Hard resynchronization is the process of transferring a consistent
complete image of the master partitions being replicated to the slave
DBEnvironment.


          Figure 1-1.  ALLBASE/Replicate Configuration Overview 

Multiple ALLBASE/Replicate Configurations 

You can develop many different ALLBASE/Replicate configurations, each a
different combination of entire DBEnvironments or subsets of
DBEnvironments.  Although this list is not exhaustive, some of the
possible configurations you can implement are listed below.  This list
briefly describes each numbered configuration illustrated in Figure 1-1
.

   1.  An entire master DBEnvironment is replicated to a dedicated slave.

   2.  A subset of a master DBEnvironment is replicated to a dedicated
       slave.

   3.  A subset of DBEnvironment A is replicated to DBEnvironment B,
       while a completely different subset of DBEnvironment B is
       replicated to DBEnvironment A. This is called two-way replication.

   4.  A series of DBEnvironments are arranged in a "cascade"
       configuration.

   5.  Several master DBEnvironments (or their subsets), each at
       different locations, are replicated to one slave DBEnvironment
       that gives a global view of the entire enterprise.

   6.  Several DBEnvironments at remote locations are involved in two-way
       replication with a DBEnvironment maintained at the headquarters
       location.

MPE/iX 5.0 Documentation