Reservations

Nobody checks out to write. Everyone can upload into a draft, name versions and release, unless someone else has reserved the branch.

A reservation says "hands off, I'm on it". The editor takes one when it opens and gives it back when you leave. A reservation runs out unless it's renewed: after 30 minutes by default (LEASE_TTL_MINUTES). The editor renews it while it's open. Close the browser tab with the editor open and the reservation stays until it runs out.

Why reserve for the editor and not for an upload? A single upload is guarded by its ETag. The web app sends If-Match, so an upload based on an older draft gets a 412 instead of overwriting someone's work. An editing session takes hours, and its result can't be merged with anyone else's, so the PDM reserves up front.

Reservations are per branch. If someone has main reserved, branch and work there.

Working offline

The exception to "nobody checks out": you want to work on a part in your own CAD, away from the PDM. Download the source from Files, Reserve the branch so nobody saves over it meanwhile, work, Upload the result, Give back. Renew the reservation if it takes longer than its time runs. The editor needs none of this.