Connections Between Replication Servers and Data Servers

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

When you set save_interval for a physical or logical connection between a Replication Server and a data server and database, you allow Replication Server to save transactions in the DSI queue. You can restore the backlogged transactions using sysadmin restore_dsi_saved_segments. See Replication Server Reference Manual > Replication Server Commands > sysadmin restore_dsi_saved_segments.

You can use these saved transactions to resynchronize a database after it has been loaded to a previous state from transaction dumps and database dumps.

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.

For example, in this figure, if the replicate data server SYDNEY_DS that is connected to Replication Server SYDNEY_RS experiences a failure, it can obtain the messages saved in the DSI queue at SYDNEY_RS to resynchronize the replicate database after it has been restored.

You can also use save_interval for setting up a warm standby of a database that holds some replicate data or one that receives applied functions.