> For the complete documentation index, see [llms.txt](https://manual.docs.microstream.one/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://manual.docs.microstream.one/4.0/data-store/customizing/optional-storage-manager-reference-in-entities.md).

# Optional Storage Manager Reference in Entities

{% hint style="warning" %}
**This is the manual for older MicroStream versions (Version < 5.0).**

**The new documentation (Version >= 5.0) is located at:**

[https://docs.microstream.one/](https://docs.microstream.one/manual)
{% endhint %}

When a reference to the loading storage is needed in entities, e.g. usage of different tenants or to store its internal state in a tailored fashion, this can be done by this little trick.

If an entity type contains one or more transient fields with field type compatible to `Persister`, the updating processing during loading will set the `Persister` instance (e.g. an `EmbeddedStorageManager` instance) used to load the entity instance to those fields.

The fields must be transient to exclude them from the persistent form of the entity.\
Checking for transient fields is only the default implementation. The checking logic can be customized via `PersistenceFoundation#setFieldEvaluatorPersistable`.

A more precise check for `Persister` fields can be customized via `PersistenceFoundation#setFieldEvaluatorPersister`.\
Note, however, that the check for compatibility with the `Persister` type is done in any case to avoid inconsistencies/crashes.

If no applicable field is found, nothing happens and no additional meta data is kept in memory. This feature is completely optional.

```java
class MyEntity
{
	String name ;
	int    value;
	
	transient EmbeddedStorageManager storage;
}
```

Upon loading an instance of class `MyEntity`, a reference to the `EmbeddedStorageManager` used to load it is set to its field `storage`.


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