# Limitations and Considerations

The following limitations apply:

* UPDATES to primary key fields are not supported. To update the field, define it as a unique index instead.

* For providers that do not support batch operations, you must manually add the `RowByRow=true` internal parameter according to the instruction provided in [Setting Change Processing parameters](https://help.qlik.com/en-US/replicate/May2025/Content/Replicate/Shared/set_up_change_processing.htm).

* The [Start from timestamp](https://help.qlik.com/en-US/replicate/May2025/Content/Global_Common/Content/SharedEMReplicate/Tasks%20at%20Runtime/monitor_detailed_run_options.htm) run option is supported only if there is a single context column defined in the [Change Processing tab](https://help.qlik.com/en-US/replicate/May2025/Content/Replicate/Shared/set_up_change_processing.htm), and its type is TIMESTAMP.

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

* Replicating data with 4-byte emoji characters is not supported.