mbt-stc

A plugin for MBT (mbt) 3 that restarts a project's started task on MVS 3.8j and compresses its development library on the way.

Why

mbt deploy puts new load modules into the project's development library (NAME.DEV.LINKLIB) by replacing members, so a running server keeps the library open while it is deployed into. A replaced member's old space is not freed, though: it stays dead until the library is compressed, and every deploy uses more of the library. A compress needs the library to itself, which only happens while the server is down. The moment to compress is therefore the restart that activates the new modules anyway.

Quick start

Declare the plugin in mbt.toml:

[plugins]
"mvslovers/mbt-stc" = "^0.1"

Then mbt deps, and after a deploy:

$ mbt deploy
$ mbt run restart

mbt run restart names the started task after the project (ufsd → UFSD). Give another name after --:

$ mbt run restart -- HTTPD

mbt run --dry-run restart shows what it would do and touches nothing.

What it does

1. Submits a compress job (IEBCOPY, COPY OUTDD=LIB,INDD=LIB) for the project's deploy target. The job asks for the library DISP=OLD. While the server holds it, MVS lets the job wait (IEF099I ... WAITING FOR DATA SETS).
2. Stops the server with P <STC>. Once it has ended, the job gets the library and compresses it.
3. Starts the server with S <STC>. The new server asks for its STEPLIB and waits in the same way until the compress is done.

MVS's data set queue does the waiting, so the command itself never polls. If the stop cannot be issued, the waiting job is cancelled (C MBTCOMP) before the command fails, so it does not hold an initiator indefinitely.

The job is submitted before the stop on purpose. A server that carries the REST API with it, such as HTTPD running mvsMF, takes the submit path down when it stops. The operator commands then fall back to the next console channel of the target (the Hercules web console) by themselves.

Requirements

• MBT 3.0.0-dev of 2026-10-10 or later. The command reads the library from ctx.project.deploy_target.
• A target (~/.mbt/targets.toml) with mvsMF for the submit. For a server that is mvsMF's own host, the target also needs a second console channel, [target.NAME.hercules].
• A job class with a free initiator for the target's jobclass. The compress job occupies it for the few seconds between submit and compress.
• Nothing installed on MVS: no procedure, no PARMLIB member.

Limits

• The started task must take its development library from STEPLIB, like every server in the ecosystem, and nothing else may hold the library while the server is down.
• The command restarts the server whether or not anything was deployed. It is meant for the restart that follows a deploy.

Licence

MIT, see LICENSE.