z Systems Processor Resource/Systems Manager Planning Guide SB10-7162-01 This is the relevant sentence:
"In support of 2 GB large pages, first introduced on the zEC12 models, all logical partition origins and limits must be on a 2 GB boundary. In other words, the addressing range assigned to the LP will start and end on a 2 GB (2048MB) boundary." So if the Initial + Reserved storage in a partition's profile does not add up to 2 GB multiple, LPAR adds enough unassigned storage to the addressing range to make things add up to a 2 GB multiple. That does not mean that the granularity for assigning storage to a zone is 2 GB. The granularity remains as documented in the table in that book. The unassigned part of the addressing range does not use any real storage (because no real storage is assigned to it). If you subsequently configure that addressing range online to the partition. LPAR assigns real storage, and now that real storage is unavailable to be assigned to other partitions. Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp. Poughkeepsie NY > >I discussed this further with Jim Mulder. The z12, where I recently >>noticed the 'unassigned' value, introduced 2 GB pages, one of whose >>consequences is that LPAR boundaries are rounded up as needed to the >>nearest 2 GB boundary. If an image profile specifies any other >>value, the 'excess' is displayed as unassigned storage. It can be >>configured online to the owning LPAR but cannot be allocated to any >>other LPAR, hence 'unassigned'. As Jim and I talked, I recollected a >>past conversation with a local CE to that effect. The LPAR in my >>display recently got 15 GB of storage added to it. The resulting odd >>value left 1 GB unassigned. > > Well this was my first tought when I saw the stroage assigned was an > odd number of GBs: Maybe the hardware assignes storage in 2GB > increments. This would explain the 1GB uassigned to align to the > next 2GB boundary. > > I usually try to verify before posting, so I looked at the z13 > Technical Guide redbook and found the table below (only parially > coied here). I read there that an LPAR having less than 256GB of > mainstorage (yours) will have a granularity of 512MB. Well, I > thougth, wrong trace, and did not post. > > After your post, either I misinterpret the table in the redbook > (most probably) or the table is in error (not likely). So the table > must indicate the minimum amount of storage that can be varied > online or offline depending on the total amount of storage assigned. True? > > Table 3-7 > Logical partition main storage granularity > Logical partition: > Largest main storage amount.............Main storage granularity > -----------------------------------..............-------------------------------- > Main storage amount > <= 256 GB ..........................................512 MB > > 256 GB < > main storage amount > <= 512 GB ..........................................1 GB > > 512 GB < > main storage amount > <= 1 TB ................................................2 GB ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
