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SQL Anywhere 11.0.1 (Français) » SQL Remote » SQL Remote Deployment and Administration » SQL Remote Administration » Understanding the Guaranteed Message Delivery System

 

Resending lost or corrupt messages

The SYSREMOTEUSER system table contains two columns that manage resending messages:

  • resend_count column   A counter that keeps track of the number of times that the subscriber database has lost messages.

  • rereceive_count column   A counter that keeps track of the number of times the Message Agent (dbremote) has determined that messages from a publisher user have been lost.

When messages are received in the proper order at a subscriber database:

  1. The subscriber Message Agent (dbremote) applies the messages in the correct order and updates its SYSREMOTEUSER system table.

  2. The subscriber Message Agent (dbremote) sends a confirmation message to the publisher.

  3. When the publisher receives the confirmation, its Message Agent (dbremote) updates its SYSREMOTEUSER system table.

When messages are not received in the proper order:

  1. The subscriber Message Agent (dbremote) sends a resend request and increments the rereceive_count value in its SYSREMOTEUSER system table.

  2. When the publisher receives the resend request, it increments the resend_count value in its SYSREMOTEUSER system table for the subscriber.

  3. In the publisher's SYSREMOTEUSER system table, the log_sent value is set to the value in the confirm_sent column. Resetting of the log_sent value causes operations to be resent.

See also