US 5,682,513 A · Cache queue entry linking for DASD record updates

Abstract

A data storage system provides disaster recovery capability by asynchronously transmitting record updates to a secondary site in sequence consistent order. Such record updates are stored at a primary site in a cache memory of a storage controller. A circular queue is created having a head pointer for locating a first (or oldest) record update with subsequent record updates of a track being linked therefrom in sequence consistent order. A tail pointer of the circular queue points to the last record update. A counter field is provided in a track slot header for counting a number of updated records in the track and hence the circular queue. When a data mover in the host processor at the primary site reads record updates for transmission to the secondary site, the data mover starts with the record update pointed to by the head pointer such that the data mover moves through the circular queue (and hence the record updates) in a backward chain fashion. The counter is decremented as each record update in the track is read by the data mover such that when the counter reaches zero the data mover knows that no other record updates exist for that track.

Claims11

Dependent claims

A storage controller in a data storage system for linking, in a backward chain using a circular queue, a plurality of record updates in a first track, said data storage system including a host processor coupled to said storage controller and running an application generating the plurality of record updates, and a direct access storage device (DASD) coupled to said storage controller for storing said plurality of record updates, said storage controller comprising:

a storage path for directing record updates between said DASD and said host processor;
and
a cache memory coupled to said storage path for storing a first track slot, said first track slot storing a first track including the plurality of record updates, said cache memory further storing a first track slot header corresponding to said first track slot and having a Q counter for counting a number of records updated in said first track slot and having a Q anchor pointer for referencing an entry in the circular queue, wherein the circular queue contains one entry for each record update of said plurality of record updates, each entry including a Q Type field, a data pointer, and a Q Chain pointer, each entry further linked to form the backward chain and to maintain an order consistent with a sequence in which the record updates are made.

Dependencies are inferred from the claim text.

Cache queue entry linking for DASD record updates

Life of this patent

Cache queue entry linking for DASD record updates

Life of this patent

Abstract

Claims11