Support for concurrent uCode update on DS8000 FCP-attached SCSI disks for 21CS VSEn customers

Currently, based on very old experiences with IBM z/VSE and DS8000 uCode upgrades, on the Customer "Must-Read" Information for DS8000 Code Updates https://www.ibm.com/support/pages/node/6585326 for example IBM DS8900F Microcode Customer Information v1.17 https://www.ibm.com/support/pages/system/files/inline-files/DS8900F%20Customer%20Information%20V117_3.pdf z/VSE (and VSEn) customers are told:

z/VSE does not support concurrent microcode upgrades for FCP-attached SCSI disks. 

Please ensure that the following steps are performed: 

1. Shutdown the z/VSE system(s) 

2. Allow IBM to perform the microcode upgrade 

3. IPL the z/VSE system(s) 

This recommendation includes all dependent z/VSE systems, e.g., those z/VSE systems that use the same lock file.

This is an issue in term of business continuity and availability for VSEn customers, since it forces VSEn customers every time that they need to upgrade their DS8000 uCode to have a downtime in their VSEn environment. 

Given that there have been improvements in VSEn storage handling and path recovery, we, 21CS VSEn, would like to jointly with the IBM DS8000 Storage team, evaluate if VSEn can support DS8000 concurrent uCode upgrade, by having VSEn in the same environment where DS8000 does their tests for concurrent uCode upgrade for z/OS, so that we can jointly decide to support it, if the equivalent DS8000 uCode concurrent upgrade tests passed by z/OS are passed by VSEn, or to improve VSEn if any of those test that are passed by z/OS are not passed by VSEn.