Patent ID: 7720864

Claim:
A computer-implemented method, comprising: in response to a metadata server receiving a data access request from one of a plurality of clients, the metadata server: determining a maximum expiration time indicated by a next scheduled time for exclusive access; wherein the data access request is for data that is also accessible by one or more other clients of the plurality of clients each having a corresponding unexpired token, and wherein said time for exclusive access is a time when exclusive access to the data is required by a task; generating an access token that grants the client access to data stored on one or more storage devices associated with the metadata server, wherein the access token comprises an expiration time, wherein the access token is one of a plurality of access tokens each provided to a respective one of the plurality of clients; and wherein said generating an access token comprises setting the expiration time of the access token to no later than the maximum expiration time indicated by the next scheduled time for exclusive access, such that the access token will be expired during the next scheduled time for exclusive access, thus preventing the client from using the access token to access the data during the next scheduled time for exclusive access, wherein at the next scheduled time for exclusive access the plurality of access tokens are expired without the metadata server transmitting a message to each client to expire its respective access tokens.