Introduced by IBM from zOS.1.8 and z9 + µcode, Group Capacity Limit (GCL) allows to set a capacity limit for a group of LPARs. When the sum of the LPARs’ R4Hs in the group reaches the GCL, all LPARs in the group are capped at the level of their share% weight in the group (and not at the levle of their DC). It allows to simplify the soft-capping management but the good thing is GCL is basic and the bad thing is GCL is basic too because of not using white space and because of the use of the weight for the capping by PR/SM. This metric is used for other things as Hard-Capping or guaranty of MSU when the server is 100%busy, so the value of the weight can be not at the right value at the right time during group capping. Here we face the same lack of flexibility as standard soft-capping.
Restrictions (*): Defined and Group Capacity
• A partition must not be defined with dedicated processors and a partition must be defined with shared processors and WAIT Completion = NO
• Hard Capping (Initial Capping) must not be defined
• z/OS must not run as a VM guest
• PR/SM capping works within ±3.6% from the defined capping value
* IBM Germany Research & Development , 2010, August