8456ch_Virtualization_Concepts.fm Draft Document for Review December 5, 2019 4:33 pm Note:  If thin provisioning is used, the metadata is allocated for the entire volume (effective,  virtual capacity) when the volume is created not when extents are used. Thin Provisioning is also possible with CKD volumes. See  IBM DS8880 Thin Provisioning  (Updated for Release 8.5) , REDP-5343, and check for APARs that are needed for certain  z/OS versions. Use of thin provisioning can affect the amount of storage capacity that you choose to order.  Use ESE capacity controls to allocate storage correctly. With the mixture of thin-provisioned (ESE) and fully provisioned (non-ESE) volumes in an  extent pool, a method is needed to dedicate part of the extent-pool storage capacity for ESE  user data usage, and to limit the ESE user data usage within the extent pool.  Also, you need to detect when the available storage space within the extent pool for ESE  volumes is running out of space. ESE capacity controls provide extent pool attributes to limit the maximum extent pool storage  that is available for ESE user data usage. They also guarantee that a proportion of the extent  pool storage will be available for ESE user data usage. The following controls are available to limit the use of extents in an extent pool: CKD Thin Provisioning Extent space efficient capacity controls for thin provisioning Figure 4-13 shows the areas in an extent pool. GLYPH<SM590000> Reserve capacity in an extent pool by enabling the extent pool limit function with the  chextpool -extentlimit enable -limit extent_limit_percentage pool_ID  command. GLYPH<SM590000> You can reserve space for the sole use of ESE volumes by creating a repository with the  mksestg -repcap capacity pool_id  command. Figure 4-13 Spaces in an extent pool 120  IBM DS8900F Architecture and Implementation Space for  normal volumes ESE Repository adjust repcap adjust %li mit Virtual volume with portion of allocated data/extents Full provisioned volumes Extent pool Virtual capacity