User's Manual

How the Message Agent for Adaptive Server
Enterprise works
This section describes how the Message Agent for Adaptive Server
Enterprise works. There are some significant differences between how the
Message Agent for Adaptive Server Enterprise and the Message Agent for
Adaptive Server Anywhere operate, which accommodate the different roles
of the two servers.
☞ For information on features of the Message Agent that are common to
Adaptive Server Anywhere and Adaptive Server Enterprise, see “Running
the Message Agent” on page 223.
Message Agent is
ssremote
The Message Agent for Adaptive Server Enterprise is the following
executable:
♦ On Windows operating systems, the Message Agent is ssremote.exe
♦ On UNIX operating systems, the Message Agent is ssremote .
Scanning the transaction log
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” on
page 265. For more information about how the Message Agent uses the
stable queue, see “Message Agent operation phases” on page 266.
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.
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