Use of HSM Exit ARCRPEXT to redirect DFSMS/hsm Tape Activity to alternative LPARS
Original Publication Date: 2001-Feb-01
Included in the Prior Art Database: 2003-Jun-19
Product Documentation "DFSMS/MVS V1R4 Installation Exits" (IBM Publication Number SC26-4908), describes the intended functionality of this exit to set a priority for a request and/or to construct messages for the Activity Log. The submitted program extends this exit to support Customer configurations that need to manage their computer installations; specifically those customers that have more shared MVS LPARS than can be supported by their tape configuration. The incorporation of this submission into the DFSMS/hsm product allows requests to DFSMS/hsm to be either queued to an alternative LPAR or deleted from the Queue. Customer Situation: Configuration consists of 36 MVS LPARs Sharing DASD. Installed Tape subsystem supported 32 systems, leaving 4 systems without tape attachment. Customer requirement was to support HSM request activity on all sharing MVS LPARs. The capability supplied in the exit would apply to any customer that has more sharing MVS LPARs than are attached to the same tape library. The exit would typically apply to Automated Tape Libraries, but this may apply to Manual Tape Library operations as well. Request Type: The exit supports three types of requests: Delete, Recall, and Recover. There are three separate sections of logic based on the type of request. Delete requests are allowed to proceed normally as there is no tape mount activity required to complete. Recover requests are denied in all cases. There is an inherent security risk with performing requested dataset recovery without explicit knowledge of the authorization granted to the requestor with respect to the dataset to be restored. The requestor is informed of this action. Recall Activity is identified, recorded in a allocated dataset that can be accessed from a sharing MVS LPAR with Tape Attachment, and then it is deleted from the request queue of the originating system. There is a follow-on process that consists of a Started Task executing a program that reads the dataset of queued requests and submits the commands to the HSM on the sharing MVS LPAR that has tape attachment to perform the recall. When the request has successfully completed, the request is removed from the dataset. The security risk for recalling migrated datasets is minimal as the requestor's authority will be checked when the dataset is OPENed (by the customer's chosen security product). Request Origination: The program checks for TSO USERs and Batch requests. In the case of TSO USERs; any information concerning ARCRPEXT exit activity is sent to the user via the TPUT Macro. Batch requests are informed of actions performed on their behalf via an MVS Console Command Interface. The JES2 command "$DM" is used to place messages into the Syslog of the requestor. There is no JES3 support in this exit.