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

The Message Agent for Adaptive Server Enterprise is the following

ssremote

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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Sybase DC38133-01-0902-01 manual How the Message Agent for Adaptive Server Enterprise works, Scanning the transaction log