Chapter 6. Principles of SQL Remote Design
containseither a single value or a comma-separated list of values.
Notthe subscriber list
AdaptiveServer Enterprise does not enter into the log a list of subscribers.
The column value is entered. All handling of subscribers is left to the
MessageAgent.
Whena table is marked for replication using sp_add_remote_table (which
callssp_setreplicate), Adaptive Server Enterprise places an entire before
imageof the row in the transaction log for deletes, and entire after image for
inserts,and both images for updates. Thismeans that the before and after
valuesof the subscription column are available.
MessageAgent actions TheMessage Agent reads the evaluated subscription expressions or
subscriptioncolumn entries from the transaction log, and matches the before
andafter values against the subscription value for each subscriber to the
publication. In this way,the Message Agent can send the correct operations
toeach subscriber.
Whilelarge numbers of subscribers do not have any impact on server
performance,they can impact Message Agent performance. Boththe work
inmatching subscription valuesagainst large numbers of subscription
values,and the work in sending the messages, can be demanding.
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