Sybase SQL Remote DC38133-01-0902-01 User Manual
Chapter 10. SQL Remote Administration
Handling of 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.
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.
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:
♦
Its resend_count.
♦
The transaction log offset of the last COMMIT in the previous message.
♦
A serial number within transactions, for transactions that span messages.
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.
applied; they are deleted. This ensures that operations are not applied more
than once.
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