Data Validation for Transactional ReplicationApril 24, 2000
Microsoft SQL Server 7.0 allow you to validate data for transactional
replication. You can specify rowcount only validation (the default) or
full checksum validation of the article data.
The process of checking replication includes the following steps: number of
lines and checksum of the table of the publisher is counted up at first,
then the similar sizes are calculated for the tables of the subscribers,
and on the basis of comparison is judged synchronisation of their
data. It is possible to do only the calculation of number of lines without
calculation of the control sum for economy of time. The process of
checking of reliability in SQL Server 7.0 proceeds in the latent mode,
i.e. it does not interrupt transactions of the publisher and the current
replication does not stop.
You can use sp_publication_validation stored procedure to validate data
for transactional replication. This stored procedure validate the data
associated with each article by calling sp_article_validation (after the
articles associated with a publication have been activated).
The sp_article_validation stored procedure invokes sp_table_validation
stored procedure, which calculates number of lines and control sum of the
published table. Then the procedure sp_article_validation inserts a call of
sp_table_validation directly into a transactional log of the publisher.
The process passes values of number of lines and control sum as parameters
in a call of sp_table_validation, written down in the transactional log.
After that Distribution Agent sends a call of sp_table_validation to the
subscribers and checks the data of the subscriber with the data of the
publisher.
The procedure sp_table_validation generates the system message, in which
is spoken about successful or unsuccessful end of check given at the
subscriber. Distribution Agent reads the system message formed by
sp_table_validation. If the check has passed successfully, the Distribution
Agent forms the system message 20575, and if the check has passed
unsuccessfully, the Distribution Agent forms the system message 20574.
Distribution Agent continues to send replications transactions to the
subscriber, even if the check has shown, that the synchronization given
of this subscriber is broken.
This utility may work in native or in character mode. If you use columns
with float data and your application has heterogeneous subscribers then
bcp utility will work in character mode and checksum on publisher and
subscriber will not equal. Not use the calculation of the control sum
in this case.
Make enabled the following replication alerts (if it is not still enabled):
- Subscriber has failed data validation
This alerts generate errors 20574 and 20575 accordingly.
 Then you will see the following:
 Check "Enabled" box and press "Apply" button.
 Choose "Yes". Make the same actions for alert "Subscriber has passed data validation".
 Then you will see the following:
 Check "Enabled" box and press "Apply" button. Then you will see the following:
 Choose "Yes". You can validate your data on a regular schedule by creating a Transact-SQL job or you can run sp_publication_validation or sp_article_validation from Query Analyzer.
 Start Snapshot Agent (if it start manually).
 If all is OK, you will receive the message 20575.
 This alert will be written in the Windows NT Application log by default.
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