Distributed File System (DFS)
DECdfs for OpenVMS is a DECnet for OpenVMS and DECnet-Plus layered product that provides OpenVMS users with the ability to use remote OpenVMS VAX, OpenVMS Alpha, and OpenVMS for Integrity server disks as if they were directly attached to the local OpenVMS system.
DECdfs software provides users and applications with transparent, high performance file access while using fewer CPU resources than standard DECnet for OpenVMS and DECnet-Plus file access.
Systems running DECdfs software can act as "servers" or "clients" or both. DECdfs servers make file resources available to systems running DECdfs client software. DECdfs clients are able to use file resources of systems running DECdfs server software. The file resources accessible through DECdfs can range in scope from a master file directory and all of its subordinate directories and files on a disk volume, to an individual file. The DECdfs server software assigns a unique name to the resource to be shared.
DECdfs has the ability to use DECdns when available or a local DFS server database. To use the local DFS server database, the access point would be registered with the /LOCAL qualifier on the DFS server node and the DFS client node must have the /NODE= qualifier specified for the MOUNT command to reference the DFS server node where the access point is being served from.
DECdfs software can use DECdns on OpenVMS VAX configurations running DECnet for OpenVMS or DECnetPlus, and on OpenVMS Alpha and OpenVMS for Integrity server configurations running DECnet-Plus. In order for DECdfs to use DECdns, there must be at least one DECdns server in the network. DECdns allows the name of the resource to be independent of its physical location on the network. DECdfs systems throughout the network can continue accessing a resource even if the resource location is changed.
The DFS server has to register the access point in the local DFS server database in order for the client to be able to specify the node name where the resource is located.
The DECdfs client uses the resource by means of the DFS$CONTROL MOUNT command. This command specifies the DECdns name by which the resource was registered or the node name registering the access point if the local DFS server database is being used, enables communication between the client and the server, and creates a pseudo-device on the client system. The pseudo-device makes the remote resource appear to the client system as a local disk. Users can then perform operations on the pseudo-device, and DECdfs handles all of the network access and translation.
Integrity: per active socket.