To synchronize distributed access to data, the File Exporter on each File Server machine distributes tokens to clients that access data from the machine. The File Exporter uses tokens to manage access to data and metadata. Tokens guarantee that each client is working with the most-recent version of the data and that multiple clients are not accessing the same data in a conflicting manner. Tokens are fully transparent to both users and administrators.
When a client such as the Cache Manager wishes to access or change a file or directory that is managed by the File Exporter, it first requests the appropriate tokens for the data from the File Exporter. The File Exporter's response to the client's request depends on the data the client wants to manipulate, the operation the client wants to perform on the data, and whether any other clients currently have tokens for the data.
If no other clients have tokens for the data, the File Exporter can issue the client the appropriate tokens. If outstanding tokens for the data exist, the File Exporter can grant the request (if no conflicts arise between the request and the outstanding tokens), revoke the existing tokens to grant the request, or consider the request pending until it can grant it. In some cases, the File Exporter simply refuses to grant the request. If the File Exporter gives the client the necessary tokens, the client in turn can access the data from the File Exporter in the fashion requested.