(Posting as answer due to long content)
Background info: I am calling lscm(scm) in builds (via ANT). The call to lscm/scm happens for more than 100 files in a component. Why I do this is to create a README file for each file from this history of change set (Work item id, summary, comment, who delivered).
Here are my findings so far:
Our RTC Server: RTC 6.0.4 iFix 005
LSCM (via Build) works on the following scenarios:
1. RTC 6.0.1 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via command line (jbe.exe).
2. RTC 6.0.4 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via command line (jbe.exe).
LSCM (via Build) FAILS on the following scenarios:
1. RTC 6.0.1 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via JSL as a windows service.
2. RTC 6.0.4 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via JSL as a windows service.
3. RTC 6.0.1 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via NSSM as a windows service.
4. RTC 6.0.4 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via NSSM as a windows service.
SCM.exe (via Build) works on the following scenarios:
1. RTC 6.0.1 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via command line (jbe.exe).
2. RTC 6.0.4 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via command line (jbe.exe).
3. RTC 6.0.1 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via JSL as a windows service.
4. RTC 6.0.4 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via JSL as a windows service.
5. RTC 6.0.1 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via NSSM as a windows service.
6. RTC 6.0.4 build tool kit + RTC 6.0.4 SCM tools and starting the build engine via NSSM as a windows service.
The above scenarios are tested on test instance
When the program runs with lscm, the whole build completes in <30 minutes.
When the program runs with scm.exe, the whole build completes in >180 mintues.
Why RTC 6.0.1 toolkit because we right now use that and plan to upgrade next week on PROD servers.