IBM LoadLeveler for AIX 5L: Using and Administering

Step 5: Specify how many jobs a machine can run

To specify how many jobs a machine can run, you need to take into consideration both the MAX_STARTERS keyword, which is described in this section, and the Class statement, which is mentioned here and described in more detail in Step 3: Define LoadLeveler machine characteristics

The syntax for MAX_STARTERS is:

MAX_STARTERS = number

Where number specifies the maximum number of tasks that can run simultaneously on a machine. In this case, a task can be a serial job step, a parallel task, or an instance of the PVM daemon (PVMD). If not specified, the default is the number of elements in the Class statement. MAX_STARTERS defines the number of initiators on the machine (the number of tasks that can be initiated from a startd).

For example, if the configuration file contains these statements:

Class = A(1) B(2) C(1)
MAX_STARTERS = 2

then the machine can run a maximum of two LoadLeveler jobs simultaneously. The possible combinations of LoadLeveler jobs are:

• A and B
• A and C
• B and B
• B and C
• Only A, or only B, or only C

If this keyword is specified in conjunction with a Class statement, the maximum number of jobs that can be run is equal to the lower of the two numbers. For example, if:

MAX_STARTERS = 2
Class = class_a(1)

then the maximum number of job steps that can be run is one (the Class statement above defines one class).

If you specify MAX_STARTERS keyword without specifying a Class statement, by default one class still exists (called No_Class). Therefore, the maximum number of jobs that can be run when you do not specify a Class statement is one.