US 8,799,569 B2Granted

Multiple enhanced catalog sharing (ECS) cache structure for sharing catalogs in a multiprocessor system

AssigneeInternational Business Machines Corporation

InventorsEric J. Harris, Franklin Emmert McCune, David Charles Reed, Max Douglas Smith

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Abstract

Various method and system embodiments for facilitating catalog sharing in multiprocessor systems use multiple ECS cache structures to which catalogs are assigned based on an attribute such as SMS storage class or a high level qualifier (HLQ) (e.g. an N-to-1 mapping) or each individual catalog (e.g. a 1-to-1 mapping). When maintenance is performed on an ECS shared catalog, the multiple ECS cache structure requires only those catalogs associated with a particular ECS cache structure be disconnected. Any catalogs in the structure that are not involved in or affected by the maintenance may be temporarily or permanently moved to a different ECS cache structure. As a result, VVDS sharing is only required for those catalogs on which maintenance is being performed or that remain associated with that ECS cache structure during maintenance. This reduces I/O activity to the DASD, and results in a significant overall performance improvement.

Claims20

Dependent claims

A method for sharing a plurality of catalogs of different data sets in a multiprocessor system, the multiprocessor system including a plurality of host systems that support an enhanced catalog sharing (ECS) function, a plurality of direct access storage device (DASD) subsystems and a coupling facility having cache structures reserved for ECS, the method comprising the steps of:

(a) connecting the ECS function in the host systems to a plurality of ECS cache structures in the coupling facility;
(b) assigning at least one catalog to each said ECS cache structure and storing a copy of an entire data volume record of said at least one catalog in the ECS cache structure, wherein the catalog is shared by the plurality of host systems, wherein the data volume record includes catalog updates, wherein the data volume record in the coupling facility is updated with the catalog updates responsive to a shared catalog request from a first host system if the shared catalog request involves a catalog update;
(c) reading the catalog updates directly from the data volume record in the coupling facility to a first host system of the plurality of host systems when the first host system needs access to the catalog;
and
(d) to perform maintenance on a particular catalog, disconnecting the ECS functions for the host systems from only the ECS cache structure that stores the data volume record of the particular catalog, and, after maintenance is performed on the particular catalog, reconnecting the ECS functions to rebuild the ECS cache structure.

2 more elements

A system for sharing a plurality of catalogs of different data sets in a multiprocessor system, comprising:

a plurality of direct access storage device (DASD) subsystems;
a coupling facility having cache structures reserved for enhanced catalog sharing (ECS);
a plurality of host systems supporting an ECS function and having cache for storing data sets, said host systems' ECS functions connected to a plurality of ECS cache structures in the coupling facility, each said ECS cache structure storing a copy of an entire data volume record of at least one catalog assigned to that ECS cache structure, wherein the catalog is shared by the plurality of host systems, wherein the data volume record includes catalog updates, wherein the data volume record in the coupling facility is updated with the catalog updates responsive to a shared catalog request from a first host system if the shared catalog request involves a catalog update;
said coupling facility configured for reading the catalog updates directly from the data volume record in the ECS cache structure to a first host system of the plurality of host systems when the first host system needs access to the catalog;
and
to perform maintenance on a particular catalog, said host systems configured for disconnecting their ECS functions from only the ECS cache structure that stores the data volume record of the particular catalog and, once maintenance on the particular catalog is completed, for reconnecting their ECS functions to rebuild the ECS cache structure.

3 more elements

Dependencies are inferred from the claim text.