Extra metadata maintained internally in `xl.meta` for a transitioned object

```
...
        "MetaSys": {
          "x-minio-internal-transition-status": "Y29tcGxldGU=",
          "x-minio-internal-transition-tier": "R0NTVElFUjE=",

	Disabled = "Disabled"
	// TransitionStatus status of transition
	TransitionStatus = "transition-status"
	// TransitionedObjectName name of transitioned object
	TransitionedObjectName = "transitioned-object"
	// TransitionedVersionID is version of remote object
	TransitionedVersionID = "transitioned-versionID"
	// TransitionTier name of transition storage class
	TransitionTier = "transition-tier"
)

		uses   bool
	}{
		{ // transitioned object version
			xlmeta: xlMetaV2Object{
				VersionID: vID,
				DataDir:   dataDir,
				MetaSys:   transitioned,
			},
			uses: false,
		},
		{ // to be restored (requires object version to be transitioned)
			xlmeta: xlMetaV2Object{
				VersionID: vID,
				DataDir:   dataDir,
				MetaSys:   transitioned,
				MetaUser:  toBeRestored,
			},

--restore-request Days=3
```

### 4.1 Monitoring transition events

`s3:ObjectTransition:Complete` and `s3:ObjectTransition:Failed` events can be used to monitor transition events between the source cluster and transition tier. To watch lifecycle events, you can enable bucket notification on the source bucket with `mc event add`  and specify `--event ilm` flag.

Note that transition event notification is a MinIO extension.

## Explore Further

	// latest can be true for delete marker or a version.
	IsLatest bool

	// DeleteMarker indicates if the versionId corresponds
	// to a delete marker on an object.
	DeleteMarker bool

	// Transitioned object information
	TransitionedObject TransitionedObject

	// RestoreExpires indicates date a restored object expires
	RestoreExpires time.Time

	// RestoreOngoing indicates if a restore is in progress

| `minio_cluster_ilm_transitioned_bytes`    | Total bytes transitioned to a tier.              |
| `minio_cluster_ilm_transitioned_objects`  | Total number of objects transitioned to a tier.  |
| `minio_cluster_ilm_transitioned_versions` | Total number of versions transitioned to a tier. |

## Cluster KMS Metrics

		return toObjectErr(errMethodNotAllowed, bucket, object)
	}
	// verify that the object queued for transition is identical to that on disk.
	if !opts.MTime.Equal(fi.ModTime) || !strings.EqualFold(opts.Transition.ETag, extractETag(fi.Metadata)) {
		return toObjectErr(errFileNotFound, bucket, object)
	}
	// if object already transitioned, return
	if fi.TransitionStatus == lifecycle.TransitionComplete {
		return nil
	}

		Host:         handlers.GetSourceIP(r),
	})

	if !remoteCallRequired && !globalTierConfigMgr.Empty() {
		// Schedule object for immediate transition if eligible.
		objInfo.ETag = origETag
		enqueueTransitionImmediate(objInfo, lcEventSrc_s3CopyObject)
		// Remove the transitioned object whose object version is being overwritten.
		os.Sweep()
	}
}

// PutObjectHandler - PUT Object
// ----------

	} else if sc, ok := fi.Metadata[xhttp.AmzStorageClass]; ok {
		objInfo.StorageClass = sc
	} else {
		objInfo.StorageClass = globalMinioDefaultStorageClass
	}

	// set restore status for transitioned object
	restoreHdr, ok := fi.Metadata[xhttp.AmzRestore]
	if ok {
		if restoreStatus, err := parseRestoreObjStatus(restoreHdr); err == nil {
			objInfo.RestoreOngoing = restoreStatus.Ongoing()

                  // This means that the state has changed since we were scheduled. This implies
                  // that an execution of runOneIteration has thrown an exception and we have
                  // transitioned to a failed state, also this means that shutDown has already
                  // been called, so we do not want to call it again.
                  return;
                }
                shutDown();