# Tracking linkage history Resource matching does not delete a `Linkage` when a grouping changes. When resources are split into separate groups, or a group drops below two members, the superseded `Linkage` is retained with its `active` field set to `false`. Current groupings have `active` set to `true`. This lets you trace how a resource's linkages have evolved over time – for example, to audit why two records were once grouped and are no longer, or to reconstruct the state of a grouping at an earlier point. Because inactive `Linkage` resources remain in the data store, use the `active` search parameter to separate current links from historical ones. Get the current linkages for a resource Return only the groupings that still hold: ``` GET /Linkage?item=Patient/patient-A&active=true&_include=Linkage:item ``` Get the historical (inactive) linkages for a resource Return the superseded groupings a resource once belonged to: ``` GET /Linkage?item=Patient/patient-A&active=false&_include=Linkage:item ``` Get the full linkage history for a resource Omit the `active` filter to return both current and historical groupings. Sort by `_lastUpdated` to follow the sequence of changes: ``` GET /Linkage?item=Patient/patient-A&_include=Linkage:item&_sort=_lastUpdated ``` Each inactive `Linkage` retains the `linkage-match-detail` extensions that recorded which identifiers caused the grouping, so you can see the specific `system|value` that once connected the resources. **Note** Inactive `Linkage` resources count toward the linkages returned by a broad search such as `GET /Linkage`. Filter on `active=true` if you want only the current view.