Additional subchannel sets

With the implementation of GDPS 4 Site, we have drastically depleted UCB's in our KPAR's and SDMPLEX, we are requesting at least 6 MSSes per LCSS in support of 4 Site and future UCB growth.

We have worked for years on UCB reclamation to comply with our 2x scale as it relates to UCB's in our one large SYSPLEX. We currently use Device Reuse in our SDM environment to address the XRC Secondary, XRC Primary for site1 and XRC Primary for Site2. On the Z13's where our SDMPLEX LPAR's are defined, we use 5 LCSS of which SDMPLEX uses 4 LCSS. For the foreseeable future, we don't see the need for additional LCSSes beyond 6. With our 4 Site implementation, things have changed considerably, we are working with IBM on several POC schedules to deliver SDM Alternate Subchannel support as well as Alternate Subchannel support for XRECOVER. IBM is delivering a lot more 4 site support but those 2 items are applicable to this request.

New requirements for 4 Site support:
• XRC secondary and XRC Secondary Swap devices will need to be accessed by all SDM LPAR's.
• Device reuse can only be used for XRC Primary to Site1 and Site2 DSSes
• SDM LPAR's need to address the XRC Sec and XRC Sec Swap and PAV's for each
• KLPAR's and Application LPARs will need access to XRC Sec, XRC Sec Swap and Flash Copy and PAV's for each
• In the future we may also want SDM LPAR access to Flash Copy and it's PAV's.


With our current environment and new requirements, we can address 6 DSSes, one smaller DSS (~14 LCU ranges for Base) and 4 large DSSes(21-28 LCU's ranges each for Base). The results of this configuration we will end up with 4 active sets by the end of 2017 and 2 future large DSSes, 21 LCU's for base which is well under our requirement for 2x scale.

We are testing and plan to implement SuperPAV's into our production environment and based on discussions with IBM it is not recommended to reduce the number of PAV's per LCU even if SuperPAV's are added.
Currently our MSS design is as follows, using the same labels IBM uses for various copies of data with MzGMM. This assumes we get XRC Primary Alternate Subchannel support for SDM and XRECOVER.

A* = Region A
B* = Region B
*1 = Site1 DASD
*2 = Site2 DASD
*F1 = Site1 DASD Flash Copy

Current MSS design:
• A1/B1 use MSS0
• A2/B2 use MSS1
• AF1/BF1 use MSS2
• PAV for A1/B1 use MSS3
• PAV's for A2/B2 use MSS3
• PAV's for AF1/BF1 use MSS2 and MSS3
What we need is support for additional MSS/LCSS and could look like this:
• A1/B1 use MSS0
• A2/B2 use MSS1
• AF1/BF1 use MSS2
• PAV's for A1/B1 use MSS3
• PAV's for A2/B2 use MSS4
• PAV's for AF1/BF1 use MSS5

We have a spreadsheet that depicts details of UCB's usage and how we would add future DSSes and also have room for Tech Refreshes. We cannot attach it to this RFE because we don't know who will be able to view it and it contains WF locations and LPAR details but can provide it to IBM upon request.