Preemptive demount in an automated storage library

Abstract

A method for selecting data storage media for demount in an automated storage library, and an automated storage library and program product therefor are disclosed. Preemptive demount of storage media is permitted when all peripheral storage devices in the library are occupied and one or more of such devices remains inactive for a predetermined time. Storage media may be demounted to service existing mount requests, provided the peripheral storage devices in which the media are mounted are inactive. There is also a need, however, to ensure the availability of an empty device to service future mount requests, particularly in libraries having only a single gripper mechanism. Thus, even when no mount requests are pending, the status of the peripheral storage devices is continually monitored. If the peripheral storage devices are all occupied, and one or more of such devices remains inactive for the predetermined time, the least recently used storage medium is demounted and transferred to a storage cell in the library.

What is claimed is: 
     
       1. A method for selecting a data storage medium for demount in an automated storage library, the automated storage library having a plurality of data storage media therein and including a plurality of internal peripheral storage devices coupled to a host processor, a plurality of storage cells, and a picker coupled to the host processor for transferring one of the plurality of data storage media between any of the plurality of internal peripheral storage devices and any of the plurality of storage cells, the method comprising the machine-executed steps of: without a pending request from the host processor access for an unmounted one of the plurality of data storage media, determining if all of the plurality of internal peripheral storage devices are occupied;   in response thereto, if all of the plurality of internal peripheral storage devices are occupied, determining if any of the plurality of internal peripheral storage devices has been inactive for a predetermined time; and   in response thereto, if any of the plurality of internal peripheral storage devices has been inactive for the predetermined time, the picker demounting one of the plurality of data storage media from one of the plurality of internal peripheral storage devices which has been inactive for the predetermined time.   
     
     
       2. The method of claim 1 wherein the aforementioned machine-executed steps are continuously repeated. 
     
     
       3. A method for selecting a data storage medium for demount in an automated storage library, the automated storage library having a plurality of data storage media therein and including a plurality of internal peripheral storage devices, a plurality of storage cells, a picker coupled to the host processor for transferring one of the plurality of data storage media between any of the plurality of internal peripheral storage devices and any of the plurality of storage cells, the method comprising the machine-executed steps of: in response to a request from the host processor to access an unmounted one of the plurality of data storage media, determining if all of the plurality of internal peripheral storage devices are occupied;   in response thereto, if all of the plurality of internal peripheral storage devices are occupied, determining if any one of the plurality of internal peripheral storage devices has been inactive for a predetermined time W; and in response thereto, if any of the plurality of internal peripheral storage devices has been inactive for the predetermined time W, the picker demounting one of the plurality of data storage media from one of the plurality of internal peripheral storage devices which has been inactive for the predetermined time W and mounting a different one of the plurality of data storage media therein according to the pending request from the host processor;     in response to determining if all of the plurality of internal peripheral storage devices are occupied, if one of the plurality of internal peripheral storage devices is unoccupied, the picker mounting one of the plurality of data storage media in the unoccupied one of the plurality of internal peripheral storage devices according to the pending request from the host processor; thereafter without a pending request form the host processor for access to an unmounted one of the plurality of data storage media, determining if any of the plurality of internal peripheral storage devices has been inactive for a predetermined time X; and   in response thereto, if any of the plurality of internal peripheral storage devices has been inactive for the predetermined time X, the picker demounting one of the plurality of data storage media from one of the plurality of internal peripheral storage devices which has been inactive for the predetermined time X.     
     
     
       4. The method of claim 3 wherein the predetermined time X is greater than or equal to the predetermined time W. 
     
     
       5. The method of claim 3 wherein the machine-executed step of the automated storage library determining if any of the plurality of internal peripheral storage devices has been inactive for a predetermined time X is continuously repeated until one of the plurality of data storage media is so demounted. 
     
     
       6. The method of claim 4 wherein the machine-executed step of the automated storage library determining if any of the plurality of internal peripheral storage devices has been inactive for a predetermined time X is continuously repeated until one of the plurality of data storage media is so demounted. 
     
     
       7. An automated storage library having a plurality of data storage media therein, the automated storage library comprising: a plurality of internal peripheral storage devices coupled to a host processor, each internal peripheral storage device capable of having one of the plurality of data storage media mounted therein;   a plurality of storage cells, each storage cell capable of storing one of the plurality of data storage media therein;   machine-controlled means for transferring one of the plurality of data storage media between any of the plurality of internal peripheral storage devices and any of the plurality of storage cells; and   machine-executed means for commanding the machine-controlled means for transferring, without a pending request from a host processor for access to an unmounted one of the plurality of data storage media, to demount one of the plurality of data storage media from one of the plurality of internal peripheral storage devices which has been inactive for a predetermined time in response to a determination that all of the plurality of internal peripheral storage devices are occupied and any of the plurality of internal peripheral storage devices has been inactive for the predetermined time, the machine-executed means coupled to the host processor and to the means for transferring.   
     
     
       8. The automated storage library of claim 7 wherein the means for transferring has only a single gripper. .Iadd. 
     
     
       9.  A program storage device readable by a computer, tangibly embodying a program of instructions executable by the computer, to perform method steps for preemptively demounting at least one data storage media from one of a plurality of internal peripheral storage devices of an automated storage library controlled by the computer, and wherein a picker demounts the data storage media and places the demounted data storage media in a storage cell, the method comprising the steps of: (a) determining if all of the internal peripheral storage devices are occupied in the absence of a pending request to access an unmounted data storage media;   (b) determining if any of the plurality of internal peripheral storage devices has been inactive for a predetermined time period; and   (c) generating instructions for the picker to demount one of the data storage media from the internal peripheral storage device which has been inactive for the predetermined time period and if all of the plurality of internal peripheral storage devices are occupied. .Iaddend..Iadd.10. The program storage device of claim 9, wherein steps (a) through (c) are performed in order. .Iaddend..Iadd.11. A program storage device readable by a system controller of an automated storage library of the type including a plurality of internal peripheral storage devices coupled to the system controller, a plurality of storage cells, and a picker coupled to the system controller for transferring one of a plurality of data storage media between any internal peripheral storage device and any storage cell, the program storage device tangibly embodying a program of instructions executable by the system controller to select one of the data storage media for demount in the absence of a pending request for an access to an unmounted one of the data storage media, the program comprising:   (a) first determining means for determining if all of the internal peripheral storage devices are occupied;   (b) second determining means for determining if any of the internal peripheral storage devices have been inactive for at least a predetermined time; and   (c) demounting means, responsive to the first and second determining means, for commanding the picker to demount one of the data storage media from one of the internal peripheral storage devices that has been inactive for at least the predetermined period of time. .Iaddend..Iadd.12. A program storage device readable by a system controller in an automated storage library, tangibly embodying a program of instructions executable by the system controller to select a data storage media for demount, the automated storage library of the type including a plurality of internal peripheral storage devices coupled to the system controller, a plurality of storage cells, and a picker coupled to the system controller for transferring one of a plurality of data storage media between any internal peripheral storage device and any storage cell, the program comprising:   (a) monitoring means, for operation without a pending request for an access to an unmounted one of the data storage media, for monitoring the internal peripheral storage devices to determine if all of the internal peripheral storage devices are occupied and if any of the internal peripheral storage devices have been inactive for at least a predetermined period of time; and   (b) demounting means, responsive to the monitoring means, for commanding the picker to demount one of the data storage media from at least one of the internal peripheral storage devices that has been inactive for at least a predetermined period of time. .Iaddend.