Using High-Availability Data Replication

High-Availability Data Replication (HDR) provides synchronous data replication for IBM Informix Dynamic Server by maintaining a backup copy of the entire database server that applications can access quickly in the event of a catastrophic failure. If one of the database servers in the replication pair fails, clients can be redirected to connect to the alternate database server. For more information on HDR, see the IBM Informix: Administrator's Guide for your database server.

HDR server pairs are composed of a primary and a secondary server. The primary server is the default server. The secondary server is read-only; update operations are not allowed.

To write application code to support HDR, follow these guidelines, which are explained in the sections below:

• Set the secondary server connection properties and enable HDR.
• Check if the server is read-only (a secondary server) and take appropriate action.
• If a connection fails, retry the connection to the alternate server and rerun the query.

You can use HDR with connection pooling. For more information, see Using High-Availability Data Replication with Connection Pooling.

Demonstration programs are available in the hdr directory within the demo directory where IBM Informix JDBC Driver is installed. For details about the files, see Appendix A. Sample Code Files.