Clarify datapoint retention docs to match purge behaviour

README.md

@@ -70,7 +70,7 @@ Try creating assets, agents, rules, users, realms, etc. using the Manager UI, pl
 ## Where's the data stored?
 
 Persistent data is stored in a PostgreSQL DB which is stored in the `openremote_postgresql-data` docker volume which is durably stored independently of the running containers (see all with `docker volume ls`).
-Note that historical attribute data is purged daily based on value of `OR_DATA_POINTS_MAX_AGE_DAYS`; this value can also be overridden for individual attributes by using the `dataPointsMaxAgeDays` configuration item.
+Note that historical attribute data is kept indefinitely by default; set `OR_DATA_POINTS_MAX_AGE_WEEKS` to purge data older than the given number of weeks.
 See the [Developer Guide](https://docs.openremote.io/docs/developer-guide/system-administration/#backuprestore) for details on making backups of the database.
 
 ## OpenTelemetry tracing

manager/src/main/java/org/openremote/manager/datapoint/AssetDatapointService.java

@@ -64,7 +64,7 @@
 /**
  * Store and retrieve datapoints for asset attributes and periodically purge data points using
  * TimescaleDB's {@code drop_chunks()} with week-based retention aligned to 7-day chunk intervals.
- * Retention defaults to inifinite.
+ * Retention defaults to infinite.
  */
 public class AssetDatapointService extends AbstractDatapointService<AssetDatapoint>
     implements ProtocolDatapointService {

model/src/main/java/org/openremote/model/value/MetaItemType.java

@@ -97,13 +97,15 @@ public final class MetaItemType {
       new MetaItemDescriptor<>("storeDataPoints", ValueType.BOOLEAN);
 
   /**
-   * How long to store attribute values in time series database (data older than this will be
-   * automatically purged).
+   * Previously set how long to store attribute values in the time series database (data older than
+   * this would have been automatically purged).
    *
    * @deprecated Per-attribute retention is no longer supported. Purging now uses TimescaleDB
    *     drop_chunks with a global week-based retention period configured via
-   *     OR_DATA_POINTS_MAX_AGE_WEEKS. This meta item is retained for backward compatibility but has
-   *     no effect.
+   *     OR_DATA_POINTS_MAX_AGE_WEEKS. For backward compatibility, the largest value of this meta
+   *     item across all attributes (rounded up to whole weeks) is used as a minimum for the global
+   *     retention period, so it can only extend how long data is kept for all attributes; it never
+   *     shortens it and has no effect when purging is disabled.
    */
   @Deprecated
   public static final MetaItemDescriptor<Integer> DATA_POINTS_MAX_AGE_DAYS =

profile/deploy.yml

@@ -358,9 +358,9 @@ services:
       # relative paths are resolved relative to OR_STORAGE_DIR
       OR_KEYCLOAK_GRANT_FILE:
 
-      # Configure the default max age for data points stored in the database (individual attributes can use a custom
-      # value by using the DATA_POINTS_MAX_AGE_DAYS AssetMeta item).
-      # OR_DATA_POINTS_MAX_AGE_DAYS: 30
+      # Configure the max age in weeks for data points stored in the database; data points are kept indefinitely when
+      # not set. The deprecated OR_DATA_POINTS_MAX_AGE_DAYS is still used (rounded up to weeks) when this is not set.
+      # OR_DATA_POINTS_MAX_AGE_WEEKS: 4
 
       # Configure the limit of data points that can be queried.
       # Defaults to 100.000. When set to 0, it disables the limit.