{
  "patent_number": "US 5682513",
  "country": "US",
  "title": "How IBM's Storage Controllers Keep Data Backups in the Right Order",
  "original_title": "Cache queue entry linking for DASD record updates",
  "summary": "A method for storage controllers to track and sequence data updates in a specific order, ensuring that remote backups remain consistent with the original data during a system failure.",
  "what_it_does": "This patent describes a way for a storage controller to manage updates to data stored on a disk. When an application updates multiple records, the controller creates a circular queue to track these changes. Each update is linked to the previous one in a backward chain, and a counter keeps track of how many updates are pending. This allows a data mover to read the updates in the exact order they occurred, which is critical for sending them to a remote site for disaster recovery without data corruption.",
  "what_it_does_not_cover": [
    "Does not cover data storage systems that lack a cache-based circular queue structure.",
    "Does not cover methods of data transmission that do not require sequence-consistent ordering.",
    "Does not cover the specific hardware architecture of the host processor itself.",
    "Does not cover real-time data replication that occurs without a staging queue."
  ],
  "filed": "1995-03-31",
  "granted": "1997-10-28",
  "expires": "2015-03-31",
  "status": "expired",
  "holder": "International Business Machines Corp",
  "holder_url": "https://patentbrief.org/company/international-business-machines-corp",
  "inventors": [
    {
      "name": "Vernon John Legvold",
      "url": "https://patentbrief.org/inventor/vernon-john-legvold"
    },
    {
      "name": "Warren Keith Stanley",
      "url": "https://patentbrief.org/inventor/warren-keith-stanley"
    },
    {
      "name": "Susan Kay Candelaria",
      "url": "https://patentbrief.org/inventor/susan-kay-candelaria"
    }
  ],
  "times_cited": 145,
  "tags": [
    "telecommunications",
    "semiconductors",
    "mechanical"
  ],
  "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.",
  "url": "https://patentbrief.org/patent/us/5682513/cache-queue-entry-linking-for-dasd-record-updates",
  "markdown_url": "https://patentbrief.org/patent/us/5682513/cache-queue-entry-linking-for-dasd-record-updates/md",
  "google_patents_url": "https://patents.google.com/patent/US5682513",
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}