As you know, I enjoy helping folks upgrade to the latest z/OS releases.  It seems I too often talk about the changes happening to existing functions the new release, more than the exploitaiton opportunities!  So, I'd like to mention a couple of "sparklers" that you can enjoy once you upgrade to z/OS V2.5, which are not rolled back in the service stream to z/OS V2.4.  

First though, let's mention, the z/OS V2.3 End of Support is September 2022, and z/OS V2.4 is not orderable since end of January 2022.    Also, this is a topic I talk about in Martin Packer's and my "Mainframe, Performance, Topics" podcast episode 30. 

Data Set File System, planned to be available in 1Q 2022.

• Allows access to MVS sequentional or partitioned data sets from z/OS UNIX, that have certain formats.
• Must be cataloged. Data set names are case insensitive.
• Popular use cases would be looking at the system log after it has been saved in SDSF, editing with vi, and data set transfers with sftp.
• Also will be useful with Ansible and DevOps tooling.
• Serialization and security is just as if it was being accessed via ISPF.
• There are mapping rules that you'll need to understand. The path will begin with /dsfs.​

Dynamic Change Master Catalog, yes, without an IPL

• Must have a valid new master catalog to switch to
• More so, you can put a comment on the command now
• Helpful if you wanted to remove imbed or replicate and you haven't been able to because it would have meant an outage.
• RACF data base encryption has a Statement of Direction.  Keep an eye out for further developments there.

For scalability:

• Increase z/OS Memory limit above 4TB to 16TB, with only 2GB frames above 4TB real. Good examples to exploit this is Java and zCX.
• More Concurrently ”Open” VSAM Linear Datasets. Db2 exploits with Apar PH09189, and APAR PH33238 is suggested.
  • Can be changed dynamically and which option you are using can be displayed.
  • The support is optional, control is with ALLOCxx’s SYSTEM SWBSTORAGE with SWA will cause SWBs to be placed in 31-bit storage, as they have been in prior releases. ATB will cause SWBs to be eligible to be placed in 64-bit storage.
  • This support moves both VSAM and allocation data areas above the bar to reduce the storage usage in the below the bar storage area.
  • Each data set is represented by several internal z/OS data areas which reside in below the bar storage.

Noteable user requirements included:

• ISPF Updates to ISPF in support of PDSE V2 member generations, and SUBMIT command to add an optional parameter SUBSYS.
• Useful for directing jobs to the JES2 emergency subsystem
• Access Method Services - IDCAMS - DELETE MASK has two new options TEST and EXCLUDE
  • Also, REPRO is enhanced to move its I/O buffers above the line to reduce the instances of out of space (878) ABENDs
  • EXCLUDE will allow a subset of objects that match the MASK to be excluded from those being deleted
  • TEST will return all the objects that would have been deleted if TEST wasn’t specified

z/OS Encryption Readiness Technology zERT

• z/OS v2.5 adds support for detecting and responding to weak or questionable connections.
• Policy based enforcement during TCP/IP connection establishment
• Immediate Termination of connections is available through policy
• Auditing via SMF records
• Notification through messages and take action with your automation
• Detect weak application encryption and take action
• Extending the Communications Server Policy Agent with new rules and actions

Of course, there are a myriad of other great enhancements rolled back to V2.4, but I wanted to give you a flavor of some of my favorite uniquely-z/OS V2.5 gems.