Best HTTP status for temporarily unavailable service due to table locking

Question

I have a service which takes a not-insignificant amount of time to complete a request. During this time, I set a status field corresponding to a table being operated on to "locked". If another request is made to this service, but the table is still "locked", I want to return the appropriate HTTP code. What would you suggest?

Answer 1

Status code 503 comes to mind (http://greenbytes.de/tech/webdav/draft-ietf-httpbis-p2-semantics-25.html#status.503)