Workload requirements

The number of logical cores defined also depends on the workload requirements and the ability of the control program or application program to effectively use multiple logical cores.

• The number of CPs required to meet the peak demands of the LP

  When a sharing LP is activated, it should be assigned enough CPs to meet its peak demands and any immediate growth requirements.

  Note: Too few CPs could limit the number of potential transactions, and too many active logical cores could affect performance. In addition to a number of initially online logical cores sufficient to meet the current peak demands of the LP, the definition should include the number of reserved logical cores required for possible growth requirements.

  For an LP that uses dedicated CPs, the number of CPs required to meet peak demand should be determined.

• The number of CPs shared by an LP

  The physical cores used by a sharing LP can be limited by the number of CPs defined to it. For example, on a six-way CPC, a two-way LP could never get more than a third of the CP resources.

  On most machines, there are many possible configurations. For example, if a two-way CPC is to be used by three sharing LPs, configuration options include all two-way LPs, all one-way LPs, or a mix of one-way and two-way LPs. PR/SM manages logical cores according to the specified processor weights.

  Three two-way LPs should only be considered if all LPs have peak demands exceeding the capacity of a one-way CPC. In this instance, the average requirements during peak periods should be examined carefully to ensure that the total does not exceed the capacity of the CPC.

  Three 1-way LPs are optimal for ITR performance and should be used if no LP has peaks exceeding half of the capacity of a two-way CPC.