Preferred techniques for transmitting on-demand data files include transmitting a first data stream in response to a first client request, and a new data stream in response to a subsequent second client request. The second client may snoop increasing amounts data from the first data stream, thereby decreasing the second client's reliance on the second data stream until the client has merged with the first data stream, at which time transmission of the second data stream will be discontinued. Alternatively, a patch data stream may be broadcast to the second client having a bandwidth less than that of the first data stream. The second client, in addition to receiving the second data stream real-time, will record data from a patch data stream until the second client has merged with the first data stream, at which time transmission of the second data stream and patch data stream will be discontinued.

A play to air controller station system in a distributed object television broadcast studio. In one embodiment, a play to air control workstation is used to control a variety of resources in a broadcast studio system interconnected by a communications network. The resources of the broadcast studio system include a transmitter unit, various media source devices such as tape decks and file servers, a network routers unit, and various decoders and encoders. The broadcast studio system is managed as a network distributed object system where an all physical devices are attached to the network either by containing appropriate software within themselves, or by attaching themselves to a computer proxy that is on the network and is able to control their functionality. The control system includes one or more device objects configured to store, route and transmit selected video segments to be aired from the television broadcast studio.

The cluster configuration database is a distributed configuration database wherein a consistent copy of the configuration database is maintained on each active node of the cluster. Each node in the cluster maintains its own copy of the configuration database and configuration database operations can be performed from any node. Configuration database updates are automatically propagated to each node in a lock-step manner. If any node experiences a failure, the configuration database uses a reconfiguration protocol to insure consistent data in each node of the cluster. The cluster configuration database uses a two-level consistency update framework to insure consistent data among the nodes. Each local configuration database uses a self-contained consistency record to uniquely identify and stamp each copy of the configuration database. The consistency of each individual copy of the configuration database can be verified from the consistency record. Additionally, the cluster configuration database uses a two-phase commit protocol to guarantee the copies of the configuration database are consistent among the nodes. Cluster operations may be performed from any node in the cluster. Cluster operations include restore, checkpoint, update, query, and consistency checking. Because each node maintains a local copy of the configuration database, configuration database queries are local operations and can be performed in parallel among the nodes. Update operations are global operations that involve each active node of the cluster. The cluster configuration database uses a global locking mechanism that implements single write/multiple reader semantics.

The invention described is a system and method for efficient scheduling of periodic phenomena including a collection of methods for modeling and selecting periodic task rates, resource schedule periods, and units of measure for the task and resource periods in scheduling systems such that the systems' schedulers may be improved with respect to performance metrics such as collision avoidance, computational efficiency, and resource utilization.

In a server that communicates with a large number of pieces of information equipment, a communication schedule between the server and the information equipment is created in an appropriate and efficient manner. Provided is an apparatus in a client-server system, having a scheduler embodied on a computer readable medium for creating a schedule, which comprises: a means for calculating a table of maximum values respectively for the number of processes for each time slot, which calculates the table of maximum respectively for the number of processes for each time slot, which is obtained by finding the respective maximum value of the number of processes performed in each time slot in a cycle of N days; and a means for calculating a time slot, which finds a time slot having the minimum value out of the maximum values obtained in the foregoing manner, in order to find a time slot in which the number of processes performed in the same time slot is brought to the minimum under the rule that the processes including communication are performed in the same time slot every N days.