[COBOL LS] Reduce number of TSO sessions started when resolving remote COPY members

[pjfarleyiii]

I would like to see many fewer TSO sessions started for a zOSMF connection to z/OS when resolving COBOL COPY members via remote retrieval with a custom zapp.yaml file. Typically I see a separate TSO session started to retrieve each COPY member for each remote library listed in the yaml file. In programs with multiple dozens or even more COPY members this can take an unusually long time and generates a separate TSO session for each library and each COPY member.

Capacity and Performance teams view this behavior very negatively and may use it to either restrict usage of the feature or even using this behavior to ban Z Open Editor access at all on already CPU-constrained systems.

Much better would be a SINGLE TSO session opened for each COPY member using a concatenated library list with all libraries in the yaml in that concatenation.

[phaumer]

@pjfarleyiii we are using z/OSMF's REST API in the way it has been implemented by the Zowe CLI team and configured in your environment. The z/OSMF has published this blog with a few tips https://community.ibm.com/community/user/blogs/hong-liang-zhao1/2020/10/13/tune-zosmf-rest-service

We started out by submitting one request at the time assuming that TSO session and address spaces would be reused on z/OS. However, many user immediately complained about the slow performance and log issues when files were not found with z/OSMF, so we introduced various parameters for parallel downloads (default is 5, you can disable by setting to 1), list-before-downloaded etc: https://ibm.github.io/zopeneditor-about/Docs/interact_zos_zopeneditor.html

However, z/OSMF is a general purpose REST API. We recommend that you try our own RSE API instead, which is a specialized service for development scenarios. It is not only better optimized for these scenarios, but also provides many additional features as shown in the presentation I attached to this discussion thread: #453 (comment)

[pjfarleyiii]

@phaumer Thank you for the prompt reply. Unfortunately I have little control over how my employer configures zOSMF. I also do not have the luxury of using your RSE API because though my employer's systems do include an RSED STC I have never been able to successfully connect to that STC. Why can't Open Editor start each COPY member retrieval TSO session with an ALLOC for a concatenated DD of ALL of the listed remote libraries and then issue one download for a member from that concatenation? Or is this a limitation of the zOSMF REST API you are using? I will try turning off the parallel downloads and also try the listBeforeDownload option to see if that improves the situation or makes it worse.