Informix HDR Setting in WebSphere Application Server

Background Knowledge*

What Is HDR (High Availability Data Replication)?

Two identical servers on two identical machines
Primary server
        Fully functional server
        All database activity – insert/update/deletes, are performed on this instance
       Automatically sends logs to secondary server
 Secondary server
       Read only server : allows read only query
        Always in recovery mode
        Receives logs from primary and replay them to keep in sync with primary
 When Primary server goes down, secondary server takes over as Standard server

HDR – Key points

Benifts:

•      Easy of administration and setup
•      Reduced downtime using DR switchover
•      Update interval
•      Automatic client redirection using DBPATH
•      Improved performance by using secondary as report server
•      Independent of geographic location
  

Limitations:

• Indexes are locked when created on primary (till they are shipped to secondary)
• No Replication of Blobspace blobs (only)
• Non logged databases are not replicated

Get your feet wet: configure the HDR in WebSphere Application Server

This section will present how to set the secondary connection properties and enable HDR in Application Server.

The following connection properties are needed to set in the connection URL:

INFORMIXSERVER_SECONDARY = secondary_server;
PORTNO_SECONDARY = secondary_portnumber;
IFXHOST_SECONDARY = secondary_hostmachine;
ENABLE_HDRSWITCH = true;

To set those properties, start the WAS server, and navigate to JDBC providers > Informix JDBC Driver > Data sources > Informix JDBC Driver DataSource > Custom properties, under the Custom properties, you could set HDR properties through “New” bottom. You have to add “ifx” before each property, for example:

ifxENABLE_HDRSWITCH     true
ifxPORTNO_SECONDARY     12345
ifxIFXHOST_SECONDARY    hostname_of_secondary
ifxINFORMIXSERVER_SECONDARY   dbserver_name_of_secondary

Now, you could start to test the failover which works for me.

Resources:

JDBC Driver Programmer's Guide (Page 2-24)

 * Informix High Availability Features -- John F. Miller III