Managing the Number of Server Instances per Server Address Space

A server address space contains one or multiple server instances which all select work requests from a work queue. Without using the new interface IWMSINF, the server address space must tell WLM during start up how many server instances will be started (parameter: PARALLEL_EU on IWM4CON).

The new interface IWMSINF allows the application to obtain the number of server instances from WLM. The following Figure 18 shows an example on how the server manager address space can use IWMSINF.

Figure 18. Exploiting IWMSINF

1. To use the new interface, the server manager address space connects to WLM with IWM4CON specifying the option MANAGE_TASK=YES. All server address spaces which connect to the same application environment must specify the same setting of MANAGE_TASK. The options SERVER_MANAGER=YES and SERVER_TYPE=QUEUE have to be defined, too.
2. After connecting the server manager address space must invoke the new service IWMSINF to obtain the number of server instances to be started initially.
3. The server adddress space starts the server instances which select work from WLM by using IWM4SSL.
4. The server manager address space reinvokes IWMSINF again to "listen" for recomendations from WLM for the number of tasks to start.
5. IF WLM wants to terminate one or multiple server instances, it resumes IWM4SSL with a new return code telling the server instance to terminate.
6. If WLM wants to terminate the server address space, it resumes IWM4SSL and IWMSINF with return code that tells the server to terminate.