5.3.1 Determining the unit of hot standby processing (server)
HA Monitor performs hot standby processing in units of servers. This subsection explains servers.
A server is a program that performs a job. Whether a single program or a group of multiple programs is to be handled as one server depends on the jobs performed in the hot-standby configuration.
- Organization of this subsection
(1) Relationship between servers and programs
Two methods are available. In one, a single program corresponds to a single server. In the other, a group of multiple programs correspond to a single server.
If you run servers in the server mode, you must use the one program per server method.
If you run servers in the monitor mode, you can choose either method. If a program that performs a job uses a shared resource, that shared resource is connected and disconnected for each server. Therefore, you must provide shared resources for each server. Furthermore, if you run servers in the monitor mode, you must create a server start command for each server. Consider these points before you choose the relationship between servers and programs.
(2) Number of servers
HA Monitor allows a maximum of 128 servers to be placed on a single host. The default setting is 16. If you place more than 16 servers, you must specify a maximum number of servers with the servmax operand in the HA Monitor environment settings.
If you use HA Monitor Extension, you can change the maximum number of servers. For details, see 3.7.1 Changing the maximum number of servers.
(3) Number of programs (when using the program management function)
If you run servers in the monitor mode and you use the program management function, you can specify the number of programs that will use the program management function and that can run concurrently on a single host. HA Monitor supports a maximum of 256 programs that use the program management function and that can run concurrently on a single host.
Specify the maximum number of programs in the pgmmax operand in the HA Monitor environment settings. Make sure that you specify the pgmmax operand value because the default value for this operand is 0.
For details about the program management function, see 3.6 Function for controlling programs (monitor mode).
(4) Considerations when the server operating methods (server and monitor modes) differ
When you place a server on a host, there is no need to determine whether the server is to be run in the server mode or monitor mode. You can place servers in the server mode intermixed with servers in the monitor mode on the same host. You can also group multiple servers together.