Abstract: A method, system, apparatus and computer program product for determining an optimal file operational time in a data storage system for use with a tape media storing data in a serpentine pattern on tape media is provided. The operational time is optimized based on a “sequence on tape” algorithm, a “minimum reversal of direction on tape” algorithm, or a “minimum delay to next data” algorithm. A model is used to determine the predicted performance of each of the algorithms, and the algorithm that provides the minimum overall operational time is chosen and applied for carrying out an operational process on the tape media.

Abstract: A method for providing continuous access to shared tape drives from two virtual tape server (VTS) nodes is disclosed. A group of tape drives are connected to two VTS nodes via a set of switches. Both VTS nodes can concurrently process requests to mount physical tape cartridges to separate tape drives. The selection of a tape drive to fulfill a volume mount request on a physical volume begins by locking down any access to a tape drive table having a composite view of all the tape drives shared between the two VTS nodes. An available tape drive is then selected to mount the physical volume, and an entry in the tape drive table is updated to claim ownership of the tape drive. A reservation command is sent to the tape drive to lock down any access to the tape drive, and the lock to the tape drive table is released. Having claimed ownership to the tape drive, the VTS node can now perform the volume mount request.

Abstract: A method to write information to two virtual tape servers. The method writes a file to a virtual host device disposed in a first virtual tape server, where the virtual host device comprises an adjustable bandwidth. The method queues a job to copy the file to a second virtual tape server, determines the age of the copy job, and copies that file to the second virtual tape server. The method sets an age threshold, and determines if the copy job age is greater than that age threshold. If the copy job age is greater than the age threshold, then the method decreases the adjustable bandwidth, if not, the method restores the adjustable bandwidth.

Abstract: An increase in the efficiency of copy operations in a data storage system is provided. A host device directs that a volume of customer data be stored through one of two virtual storage servers on media in an associated library. An initiating controller queues a request to copy the volume to a second library. If the request is not processed by the initiating controller within a predetermined period, the initiating controller broadcasts the copy request to other controllers, each of which queues the request. After one of the controllers processes the request and the volume has been copied to the second library, the processing controller broadcasts a message to the other controllers which then dequeue the copy request from their respective copy queues. Upon receipt of such message, the initiating controller transmits a message to the host device that the volume was successfully stored and copied.

Abstract: A method, system, apparatus and computer program product for determining an optimal file operational time in a data storage system for use with a tape media storing data in a serpentine pattern on tape media is provided. The operational time is optimized based on a “sequence on tape” algorithm, a “minimum reversal of direction on tape” algorithm, or a “minimum delay to next data” algorithm. A model is used to determine the predicted performance of each of the algorithms, and the algorithm that provides the minimum overall operational time is chosen and applied for carrying out an operational process on the tape media.

Abstract: A method for providing continuous access to shared tape drives from two virtual tape server (VTS) nodes is disclosed. A group of tape drives are connected to two VTS nodes via a set of switches. Both VTS nodes can concurrently process requests to mount physical tape cartridges to separate tape drives. The selection of a tape drive to fulfill a volume mount request on a physical volume begins by locking down any access to a tape drive table having a composite view of all the tape drives shared between the two VTS nodes. An available tape drive is then selected to mount the physical volume, and an entry in the tape drive table is updated to claim ownership of the tape drive. A reservation command is sent to the tape drive to lock down any access to the tape drive, and the lock to the tape drive table is released. Having claimed ownership to the tape drive, the VTS node can now perform the volume mount request.

Abstract: A method to write information to two geographically separated virtual tape servers, where the method provides a file to a virtual tape controller, writes that file to a first virtual tape server, and queues a copy job for the file in the virtual tape controller. Subsequently, the method provides the file to a second virtual tape server. The method sets a throughput threshold, determines the actual VTC throughput, and determines if the actual VTC throughput exceeds the throughput threshold. The method sets an age threshold and determines if the copy job age is greater than that age threshold. If the actual VTC throughput is greater than the throughput threshold and the copy job age is greater than the age threshold, then the method decreases the first adjustable host bandwidth and/or the second adjustable host bandwidth, otherwise the method restores the bandwidth to a nominal value.

Abstract: An apparatus, system, and method are disclosed for recalling a logical volume from a mountable media for use in a virtual tape server. The apparatus includes a receiving module, a queuing module, and an optimizer module. The receiving module receives recall requests for logical volumes stored in a mountable media such as a tape cartridge. The queuing module places the requests in a queue to be processed in turn. The optimizer module reorders the queue based on one or more optimization rules in order to process the recall requests more efficiently.

Abstract: Method, apparatus and computer program product are provided to increase the efficiency of copy operations in a data storage system. Multiple virtual storage controllers are each in communication with a host device and to two virtual storage servers. Both virtual storage servers are attached to a respective automated storage library. Each controller includes a copy queue. After directing that a volume of customer data be stored through one of the servers on media in the associated library, an initiating controller queues in a copy queue a request to copy the volume to the other library. If the request is not processed by the initiating controller within a very short period, the initiating controller broadcasts the copy request to the other controllers. Preferably, the copy request is transmitted first from the initiating controller to a routing device in one of the servers which broadcasts the request to each other controller. The copy request is queued in a copy queue of each other controller.

Abstract: A method to write information to two virtual tape servers. The method writes a file to a virtual host device disposed in a first virtual tape server, where the virtual host device comprises an adjustable bandwidth. The method queues a job to copy the file to a second virtual tape server, determines the age of the copy job, and copies that file to the second virtual tape server. The method sets an age threshold, and determines if the copy job age is greater than that age threshold. If the copy job age is greater than the age threshold, then the method decreases the adjustable bandwidth, if not, the method restores the adjustable bandwidth.

Abstract: A method is disclosed to write information to two geographically separated virtual tape servers, where a first virtual server includes a first adjustable host bandwidth, and where a second virtual tape server includes a second adjustable host bandwidth, and where the first virtual tape server and the second virtual tape server exchange information via a virtual tape controller. The method provides a file to the virtual tape controller, writes that file to the first virtual tape server, and queues a copy job for the file in the virtual tape controller. Subsequently, the method provides the file to the second virtual tape server. The method sets a throughput threshold, determines the actual VTC throughput, and determines if the actual VTC throughput exceeds the throughput threshold. The method sets an age threshold and determines if the copy job age is greater than that age threshold.

Abstract: An error recovery process for a non-synchronous DASD control unit. A channel process within the control unit is able to operate on different fields from a device process within the control unit. Independent errors may be sensed by each process. The error recovery process provides for restarting only the trailing process and deferring handling of the error sensed by the leading process, whenever possible.

Abstract: A cached DASD peripheral subsystem is operated in a so-called non-synchronous mode, that is, device operations are not synchronous to the host processor operations. A rate-changing buffer is interposed between the channel attachment for the host processor and the DASD, preferably having a storage capacity for one full DASD track of data. The rotational position for the data records being transferred in either direction, i.e., write or read, are kept in the rate-changing buffer to be kept with the record being transferred through the rate-changing buffer. Each time the peripheral subsystem supplies ending status to the host processor and all records to be transferred are retentively stored in DASD, a record control field and the rotational position of the last record transferred in a chain of commands being transferred the rotational position of such last record, its type, and other control data are stored in a control store separate from any cache directory or track directory in cache.

Abstract: A control unit for DASD operation to transfer data between the device and a buffer and between a channel and a buffer. In that manner the channel and device are enabled to transfer data independently of each other. Mechanisms are provided for communication between the channel interface process in the control unit and the device interface process in the control unit. Some of these mechanisms are stored with the record in the buffer and others are stored in control storage. Principle communicating mechanisms include a device record pointer, a channel record pointer, a next operation field, a device state indicator, record control flags, and two buffer pointers.