Routes Between Replication Servers

You can set save intervals for routes between Replication Servers for recovery of messages.

If the Replication Server has suspended routes, or if a network or data server connection is down, a backlog of messages may accumulate in the Replication Server stable queues. The chance of recovering these messages decreases with time. Source Replication Servers may already have deleted messages from their stable queues and database logs may already have been truncated.

When you set the save_interval parameter for each route between Replication Servers, you allow each Replication Server to retain messages for a minimum period of time after the next site in the route acknowledges that it has received the messages. The availability of these messages increases the chance of recovering online messages after queues are rebuilt.

For example, in this figure, Replication Server TOKYO_RS maintains a direct route to MANILA_RS, and MANILA_RS maintains a direct route to SYDNEY_RS.

Save Interval Example

Figure 7-1 illustrates an example of save interval in a Replication System. In this example, there is a primary and a replicate data server, as well as, three Replication Servers in different locations. The Replication Server tokyo underscore R S maintains a direct route to manila underscore R S, and manila underscore R S maintains a direct route to sydney underscore R S. tokyo underscore R S retains messages for a period of time after manila underscore R S has received them. If manila underscore R S experiences a partition failure, it requires that tokyo underscore R S to resend the backlogged messages. manila underscore R S can also retain messages to allow sydney underscore R S to recover from failures.

TOKYO_RS retains messages for a period of time after MANILA_RS has received them. If MANILA_RS experiences a partition failure, it requires that TOKYO_RS to resend the backlogged messages. MANILA_RS can also retain messages to allow SYDNEY_RS to recover from failures.

When all of the messages stored on a stable queue segment are at least as old as the save_interval setting, Replication Server deletes the segment so it can be reused.