User's Manual

Synchronizing data over a message system
Creating subscriptions A subscription is created at a consolidated Adaptive Server Enterprise
database using the sp_subscription procedure with a first argument of
create.
Creating a subscription defines the data to be received. It does not
synchronize a subscription (provide an initial copy of the data) or start
(exchange messages) a subscription.
Synchronizing
subscriptions
Synchronizing a subscription causes the Message Agent to send a copy of all
rows in the subscription to the subscriber. It assumes that an appropriate
database schema is in place. At an Adaptive Server Anywhere consolidated
database, subscriptions are synchronized using the SYNCHRONIZE
SUBSCRIPTION statement. At an Adaptive Server Enterprise consolidated
database, subscriptions are synchronized using the sp_subscription
procedure with a first argument of synchronize.
When synchronization messages are received at a subscriber database, the
Message Agent replaces the current contents of the database with the new
copy. Any data at the subscriber that is part of the subscription, and which
has not been replicated to the consolidated database, is lost. Once
synchronization is complete, the subscription is started by the Message
Agent using the START SUBSCRIPTION statement or sp_subscription
procedure with a first argument of start.
Large volume of messages may result
Synchronizing databases over a message system may lead to large volumes
of messages. In many cases, it is preferable to use the extraction process to
synchronize a database locally without placing this burden on the message
system.
Synchronizing
subscriptions during
operation
If a remote database becomes out of step with the consolidated database, and
cannot be brought back in step using the SQL passthrough capabilities of
SQL Remote, synchronizing the subscription forces the remote database into
step with the consolidated database by copying the rows of the subscription
from the consolidated database over the contents at the remote database.
Data loss on synchronization
Any data in the remote database that is part of the subscription, but which
has not been replicated to the consolidated database, is lost when the
subscription is synchronized. You may wish to unload or back up the
remote database using Sybase Central or, for Adaptive Server Anywhere,
the dbunload utility before synchronizing the database.
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