{
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-12",
  "slug": "scsi-unit-attention",
  "term": "SCSI Unit Attention",
  "aliases": [
    "UNIT ATTENTION"
  ],
  "definition": "SCSI Unit Attention is a condition that notifies an initiator of a relevant logical-unit or target state change.",
  "note": "Identity: Its sense key is 06h, distinct from CHECK CONDITION status 02h. ASC/ASCQ qualifies the change: 29h/00h combines power-on and reset possibilities, while 2Ah/09h reports changed capacity data. These codes do not isolate a failed component. [t10-keys] [t10-asc]\n\nObservation: In Linux v6.12 target code, pending conditions are held on an initiator-mapped device entry. The REQUEST SENSE clearing helper selects the first queued pair, described by the code as highest priority, and removes all pending conditions from that entry. This is a version-specific implementation, not a universal device rule or a passive event-history query. [linux-target-ua]\n\nHandling: Linux v6.12 can select a retry for an expected reset notification, but preserves the 28h/00h medium-change exception in that branch. Do not infer an unconditional retry policy from the key alone. [linux-error]\n\nResponse length: In that same target implementation, a request with the DESC bit set is rejected before the clearing helper runs. Buffer-mapping failure also returns before that helper. Once reached, the helper clears pending conditions before the length-limited payload copy. A short successful response therefore need not retain every field needed to interpret the consumed notification. [linux-target-sense]\n\nIdentity query: The cited SCSI reference specifies that INQUIRY runs without clearing a pending Unit Attention. An identity response is therefore not evidence that the notification was consumed. Its UA_INTLCK_CTRL table separately distinguishes clearing from retention after CHECK CONDITION reporting; clearing policy is device-dependent. That retention does not make REQUEST SENSE non-consuming: Table 454's footnote says it still clears the reported condition. [seagate-ua-policy]",
  "related": [
    "scsi",
    "scsi-sense-data",
    "scsi-sense-key",
    "scsi-check-condition",
    "additional-sense-code",
    "additional-sense-code-qualifier"
  ],
  "citations": [
    {
      "id": "t10-keys",
      "title": "T10 SCSI sense-key assignments (informative, dated 18 May 2012)",
      "url": "https://www.t10.org/lists/2sensekey.htm",
      "accessed": "2026-10-26"
    },
    {
      "id": "t10-asc",
      "title": "T10 ASC/ASCQ assignments, list dated 28 November 2024",
      "url": "https://www.t10.org/lists/asc-num.txt",
      "accessed": "2026-10-26"
    },
    {
      "id": "linux-target-ua",
      "title": "Linux v6.12 target: target_scsi3_ua_check and core_scsi3_ua_clear_for_request_sense",
      "url": "https://github.com/torvalds/linux/blob/v6.12/drivers/target/target_core_ua.c",
      "accessed": "2026-10-26"
    },
    {
      "id": "linux-error",
      "title": "Linux v6.12: scsi_report_sense and scsi_check_sense; disposition is not device command status",
      "url": "https://github.com/torvalds/linux/blob/v6.12/drivers/scsi/scsi_error.c",
      "accessed": "2026-10-26"
    },
    {
      "id": "hesela-sense",
      "title": "Hesela: SCSI state changes, sense data and Linux error interpretation",
      "url": "https://hesela.com/analyses/scsi-sense-kernel-log-signatures/#unit-attention",
      "accessed": "2026-10-26"
    },
    {
      "id": "linux-target-sense",
      "title": "Linux v6.12 target: spc_emulate_request_sense, validation and copy ordering",
      "url": "https://github.com/torvalds/linux/blob/v6.12/drivers/target/target_core_spc.c",
      "accessed": "2026-11-04"
    },
    {
      "id": "seagate-ua-policy",
      "title": "Seagate SCSI Commands Reference Rev. L (November 2020), INQUIRY p. 104 and UA_INTLCK_CTRL Table 454 p. 464",
      "url": "https://www.seagate.com/files/staticfiles/support/docs/manual/Interface%20manuals/100293068L.pdf",
      "accessed": "2026-11-12"
    }
  ],
  "provenance": [
    "T10 online assignments are informative; the applicable written standard takes precedence.",
    "No device reset, recovery test or failure-rate measurement was performed."
  ]
}