# Limitations and considerations

Using MongoDB as a source database in a Qlik Replicate task is subject to the following limitations:

* When storing changes in Change Tables, the before image will not be stored.

* When processing an UPDATE operation on the source, the most up-to-date copy of the document will be replicated to the target, For example, if three UPDATE operations were performed on a document, only the document with the last UPDATE will be replicated to target.

* Unlimited LOB size is not supported.

* Capture of new empty databases and new empty collections is not supported. A new collection must contain at least one document before it can be captured.

* [Table content filters](https://help.qlik.com/en-US/replicate/May2025/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_filters.htm) are not supported.

* Database names must be English only.

* Dropping or renaming source collections:

  * During CDC: If a source collection is renamed/dropped during CDC, it will be suspended (i.e. excluded from the replication).
  * During Full Load: If a source collection is renamed/dropped during Full Load, the task will stop.

* Dropping or renaming source databases is not supported.

* Replication of transactional audit data is not supported.

* Replication of a document in a collection that contains a reference to other documents using DBRefs is not supported.

* During CDC, when reading from a Change Stream, Replicate does not support a Change Event larger than 16 MB.