SQL Remote User's Guide
Administering SQL Remote for Adaptive Server Enterprise
How the Message Agent for Adaptive Server Enterprise works
The Message Agent scans the Adaptive Server Enterprise transaction log in order to collect transactions to be sent to remote databases. It stores these transactions in a stable queue.
For more information about the stable queue, see The stable queue. For more information about how the Message Agent uses the stable queue, see Message Agent operation phases.
The SQL Remote Message Agent uses the same transaction log scanning interface as the Adaptive Server Enterprise Log Transfer manager (LTM). Adaptive Server Enterprise maintains a truncation point, which is an identifier for the oldest page in the transaction log needed by the replication system.
The SQL Remote Message Agent sets the truncation point as soon as transactions are scanned from the transaction log and committed in the stable queue. This allows the dump transaction command to reclaim space in the transaction log as soon as possible. The Message Agent does not wait until confirmation is received from remote databases before setting the truncation point.
Message Agent must be run to reclaim log spaceThe Message Agent must be run frequently enough to prevent the transaction log from running out of space. The dump transaction command does not reclaim space from pages after the truncation point. |
Using SQL Remote on an Adaptive Server Enterprise database participating in a Replication Server setup may involve other considerations. If your database has a replication agent (LTM) running against it, then you need to use the SQL Remote Open Server as an additional component. Adaptive Server Enterprise databases have replication agents running against them in the following circumstances:
The database is participating in a Replication Server setup as a primary database, or
The database is participating in a Replication Server setup and is using asynchronous procedure calls.
If the database is participating in a Replication Server setup as a replicate site, and no asynchronous procedure calls are being used, there is no need for the SQL Remote Open Server.
For more information about the SQL Remote Open Server, see Using SQL Remote with Replication Server.