{
  "slug": "scsi-test-unit-ready",
  "term": "SCSI TEST UNIT READY",
  "aliases": [
    "TEST UNIT READY",
    "TUR"
  ],
  "definition": "SCSI TEST UNIT READY reports whether an addressed logical unit is ready for applicable operations without requesting a self-test.",
  "note": "Command: TEST UNIT READY uses opcode 00h. Its response concerns readiness, not the contents of a requested block range. Other conditions, including deferred errors, can yield BUSY or RESERVATION CONFLICT; a response is not limited to GOOD or CHECK CONDITION with sense key NOT READY. [seagate-tur]\n\nInterpretation: NOT READY can describe absent media or a logical unit becoming ready; it is not by itself a hardware-failure diagnosis. Read the status and returned sense together. [seagate-tur]\n\nDevice scope: The cited tape-library interface reports readiness to accept commands and can return CHECK CONDITION for pending Unit Attention. A library response is not a readiness result for a tape drive or its loaded medium. [oracle-tur]\n\nVerification scope: The SIGMETRICS 2007 field study distinguishes media scrubs using drive-internal SCSI VERIFY from data scrubs that read sectors and compare stored checksums. These are sector-access mechanisms, not readiness probes; the study did not measure TUR detection sensitivity. [lse-probes]",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    "A successful readiness probe does not verify stored bytes, checksum integrity, write durability or the outcome of a later operation."
  ],
  "related": [
    "scsi",
    "scsi-logical-unit",
    "scsi-check-condition",
    "scsi-sense-data",
    "scsi-unit-attention",
    "latent-sector-error",
    "data-scrubbing"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-14",
  "citations": [
    {
      "id": "seagate-tur",
      "title": "Seagate SCSI Commands Reference, Rev. H (July 2014), section 3.53 and Tables 186-187",
      "url": "https://www.seagate.com/files/staticfiles/support/docs/manual/Interface%20manuals/100293068h.pdf#page=181",
      "accessed": "2026-11-13"
    },
    {
      "id": "oracle-tur",
      "title": "Oracle SL4000 SCSI Reference: Test Unit Ready (00h)",
      "url": "https://docs.oracle.com/en/storage/tape-storage/sl4000/slksr/test-unit-ready-00h.html",
      "accessed": "2026-11-13"
    },
    {
      "id": "lse-probes",
      "title": "Bairavasundaram, Goodson, Pasupathy and Schindler. An Analysis of Latent Sector Errors in Disk Drives. SIGMETRICS 2007, sections 3.3, 4.1-4.3 and 5.5",
      "url": "https://research.cs.wisc.edu/adsl/Publications/latent-sigmetrics07.pdf",
      "accessed": "2026-11-14"
    }
  ],
  "provenance": [
    "Source review of Seagate Rev. H and the Oracle SL4000 reference; the library example is product-specific, not a universal tape-drive rule. [seagate-tur] [oracle-tur]",
    "The verification limitation is an inference from command scope. No SCSI command, device test or reliability measurement was performed."
  ]
}