Configuring automatic client reroute for client connection distributor technology

 

Distributor or dispatcher technologies such as WebSphere® EdgeServer distribute client application reconnection requests to a defined set of systems if a primary database server fails. If you are using distributor technology with DB2® automatic client reroute, identify the distributor itself as the alternate server to DB2 automatic client reroute.

You might be using distributor technology in an environment similar to the following:

Client —> distributor technology —> (DB2 Connect™ Server 1 or DB2 Connect Server 2) —> DB2 z⁄OS

where:

The client is catalogued using DThostname in order to utilize the distributor technology to access either of the DB2 Connect Servers. The intervening distributor technology makes the decision to use GWYhostname1 or GWYhostname2. Once the decision is made, the client has a direct socket connection to one of these two DB2 Connect gateways. Once the socket connectivity is established to the chosen DB2 Connect server, you have a typical client to DB2 Connect server to DB2 z⁄OS connectivity.

For example, assume the distributor chooses GWYhostname2. This produces the following environment:

Client —> DB2 Connect Server 2 —> DB2 z⁄OS

The distributor does not retry any of the connections if there is any communication failure. If you want to enable the automatic client reroute feature for a database in such an environment, the alternative server for the associated database or databases in the DB2 Connect server (DB2 Connect Server 1 or DB2 Connect Server 2) should be set up to be the distributor (DThostname). Then, if DB2 Connect Server 1 locks up for any reason, automatic client rerouting is triggered and a client connection is retried with the distributor as both the primary and the alternate server. This option allows you to combine and maintain the distributor capabilities with the DB2 automatic client reroute feature. Setting the alternate server to a host other than the distributor host name still provides the clients with the automatic client reroute feature. However, the clients will establish direct connections to the defined alternate server and bypass the distributor technology, which eliminates the distributor and the value that it brings.

The automatic client reroute feature intercepts the following SQL codes:

Note: Client reroute might not be informed of socket failures in a timely fashion if the setting of the "TCP Keepalive" operating system configurations parameter is too high. (Note that the name of this configuration parameter varies by platform.)

Parent topic: Automatic client reroute description and setup

Related reference
Automatic client reroute roadmap