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SQL Anywhere 10.0.1 » SQL Remote » SQL Remote Administration » The message tracking system

Tracking messages by transaction log offsets Next Page

Handling lost or corrupt messages

When messages are received at a subscriber database, the Message Agent applies them in the correct order (determined from the log offsets) and sends confirmation to the publisher. If a message is missing, the Message Agent increments the local value of rereceive_count, and requests that it be resent. Other messages present or en route are not applied.

The request from a subscriber to resend a message increments the resend_count value at the publisher database, and also sets the publisher's log_sent value to the value of confirm_sent. This resetting of the log_sent value causes operations to be resent.

Users cannot reset log_sent

The log_sent value cannot be reset by a user, as it is in a system table.

Message identification

Each message is identified by three values:

Messages with a resend_count value smaller than rereceive_count are not applied; they are deleted. This ensures that operations are not applied more than once.