Runtime error SAPSQL_SQLS_INVALID_CURSOR occurs when using the Mass Data Extractor (MDE)

Symptom: you schedule an extraction using /N/VDB/MDE and the background job fails:

The job fails due to a runtime error:

This happens if the following conditions apply:

1. You have SAP basis release 7.40 or later
2. You have more records to be exported than the Package Size you define
3. You did not tick the "Defer HTTP Post"
4. You are extracting to a target system through the Data Distribution Engine (DDE) -> so you are not exporting to a flat file

Reason: from basis release 7.40 and up, a SELECT-ENDSELECT loop with an (implicit or explicit) DB commit  results in a runtime error. HTTP requests do perform an implicit DB commit from basis release 7.40 and up.

Solution: make sure to tick the "Defer HTTP Post" checkbox, so the Mass Data Extractor will first save all data packages to disk (specified as the "Download directory" in the relevant transaction), and send all those to the DDA via HTTP requests, instead of from within a SELECT-ENDSELECT loop.