In this paper we focus on the issue of repository transactions. Similar to database objects repository objects can be accessed form multiple clients simultaneously. The organization of repository data however differs from that of traditional database systems. It contains multiple layers of metadata. Handling modification operations form in a multiclient environment requires an that exiting concurrency control techniques be adapted to the specifics of the repository systems. In this paper we describe a novel locking protocol for OMG MOF based repository systems. KEYWORDS Repository Systems; Metadata, Repository Transactions