Problem:

This can be caused by several reasons, in generally Mainframe Express Catalog cannot be found or opened for Write Operation.

Resolution:

Therefore, check following possible reasons in this sequence:

1. Catalog.Dat may not be Write protected by Windows, if so please uncheck Write Protection

2. Ensure path of Catalog.Dat is correctly entered in Project Settings / Catalog; a wrong path can be caused by the fact that Catalog is placed shared on a Lan Drive and Drive letter has changed

3. MFA Drag/Drop needs the complete path and filename, e.g. C:\\TEMP\\CATALOG.DAT;

For Mainframe Express itself, only the path (without Catalog name) is sufficient  e.g. C:\\TEMP\\