[Yandex Cloud documentation](../../../index.md) > [Yandex DataLens](../../index.md) > Troubleshooting > Data preparation not finished

# [Yandex DataLens] Data preparation not finished

`ERR.DS_API.DB.MATERIALIZATION_NOT_FINISHED`

Data preparation is not complete yet; wait a few more minutes or reload the data.


You get this error if file upload is not yet fully processed in the [file](../../operations/connection/create-file.md), [Google Sheets](../../operations/connection/create-google-sheets.md), or [Yandex Documents](../../operations/connection/create-yadocs.md) connection.


The error also occurs when [importing workbooks](../../workbooks-collections/export-and-import.md#import-workbook) with such connections. To fix the error, reload the data after importing the workbook.