NetBase for MPE Reference Guide

Introduction
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Other NetBase Services
Two other NetBase services are available: NetBase SQL Shadowing and NetBase Client. These
services are briefly described below but are not referenced in this guide. For reference information,
see the NetBase SQL Shadowing Handbook and the NetBase Client Reference Guide.
NetBase SQL Shadowing
In addition to the NetBase Shadowing service designed for IMAGE databases and KSAM files,
NetBase provides shadowing of ALLBASE DBEs. With NetBase SQL Shadowing, updates are
applied to shadow copies in the same order as they were applied to the master copy of the DBE. If
communication between the master and the shadow copies is interrupted, when the communication
is resumed, NetBase SQL Shadowing determines where it was in the update process, and resumes
where it left off.
You may shadow entire ALLBASE DBEs or you may shadow specific tables. Depending on which
list is shorter, you may define the tables to be excluded from or included in the shadowing process.
Using the same table specification logic, you may create partitioning, allowing different tables to be
masters on different machines. By developing vertical partitioning, you reduce the possibility of the
DBE losing synchronization.
Additional Processing
With NetBase SQL Shadowing, you are allowed additional processing before and after the network
transaction is sent from the master to the shadow machines. User exit procedures may be invoked
prior to sending the transaction to the remote nodes, prior to updating the DBE on the remote
nodes, or after an update on a remote node has failed to be applied. NetBase SQL Shadowing reads
the NetBase directory entries to determine which DBEs to shadow, which tables to include and if
user exits are to be invoked.
User exits may be used to re-route or ignore data prior to sending the transaction across the network
or after it has been received on a shadow node. A user exit may be used to log transactions without
actually sending the data to remote nodes by specifying node zero, a “pseudo-node.” Another
possibility for a user exit is to notify the console when a transaction was not successfully applied.
For more information on NetBase SQL shadowing, see the NetBase SQL Shadowing Handbook.