{
  "slug": "map-sync",
  "term": "MAP_SYNC",
  "aliases": [],
  "definition": "MAP_SYNC is a Linux mmap flag for supported DAX files that provides a file-offset persistence guarantee used with appropriate CPU persistence instructions.",
  "note": "The flag must be requested with MAP_SHARED_VALIDATE: MAP_SHARED can silently ignore it, and files without support fail with EOPNOTSUPP. It does not itself issue a persistence operation for every store. [mmap-docs] The application still needs a correct durability and recovery protocol; a mapping contract is not multi-write atomicity. [pmdk-persist]",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "related": [
    "dax",
    "persistent-memory",
    "persistence-ordering",
    "crash-consistency"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-13",
  "citations": [
    {
      "id": "mmap-docs",
      "title": "Linux man-pages. mmap(2), MAP_SYNC and MAP_SHARED_VALIDATE.",
      "url": "https://man7.org/linux/man-pages/man2/mmap.2.html",
      "accessed": "2026-10-13"
    },
    {
      "id": "pmdk-persist",
      "title": "PMDK 1.13.1. pmem2_get_persist_fn(3): early persistence and non-transactional semantics.",
      "url": "https://github.com/pmem/pmdk/blob/1.13.1/doc/libpmem2/pmem2_get_persist_fn.3.md",
      "accessed": "2026-10-13"
    },
    {
      "id": "hesela-pmem",
      "title": "Hesela. Persistent memory: DAX is not a durable commit.",
      "url": "https://hesela.com/analyses/pmem-persistence-domains-dax/",
      "accessed": "2026-10-13"
    }
  ]
}