To turn off parallel data loading for an individual file, open the file to be modified then click on File > Document Properties then click on "Compatibility Settings" and check the box for "Use serial data loading when opening this document":


To turn off parallel data loading for all files opened by an installed Spotfire client, click on Tools > Options > Document and uncheck the box for "Allow data to be loaded in parallel when opening documents":


Customers with an on-premise installation of Spotfire Server and Spotfire Analyst clients, or TIBCO Spotfire Cloud Enterprise, can also configure parallel loading at the Group level by clicking on Tools/Administration Manager and modifying one of these Preferences.  (Cannot be set in Spotfire Desktop or TIBCO Cloud Spotfire).

• Application > DataImportPreferences > ForceSerialDocumentDataLoading

or

• Application > DataImportPreferences > LoadDocumentDataInParallel

There is an inherent hierarchy to these settings, which is described below:

1. Preference Application > DataImportPreferences > ForceSerialDocumentDataLoading
Manual: "Set to True to force loading of all imported data to be done in a sequence, instead of letting data from multiple sources load simultaneously, on different threads. Default is False."

See also LoadDocumentDataInParallel.
If true, there will only be serial data loading. Period.
If false, proceed to the next setting below.

2. Preference Application > DataImportPreferences > LoadDocumentDataInParallel
Manual: "Lets you specify whether the Allow data to be loaded in parallel when opening documents check box in Tools > Options > Document should be enabled by default. This setting allows data from multiple sources to load simultaneously, on multiple threads. Default is True."

By switching to False, the default setting will be to clear the check box, but the end users can still change this setting themselves.

See also ForceSerialDocumentDataLoading.
If true, parallel data loading is allowed/used by default, but can be overridden by settings below. 
If false, parallel data loading is not used by default, but can be overridden by settings below.

3. Option Tools menu > Options > Document > Data loading > Allow data to be loaded in parallel when opening documents
Manual: "Select this option to allow imported data from different data sources to be loaded on separate threads. This setting might speed up data loading when opening a document with many data sources, and it also provides better feedback in the progress dialog, if something is slow. If the check box is cleared, all data sources are loaded in sequence, one after the other."

An administrator can switch off this setting for your organization, if required by your environment.
If true, there may be parallel data loading but can be overridden by settings below. 
If false, there will be no parallel data loading.

4. Document Properties File > Document Properties > General tab, click on "Compatibility Settings" and check the box for "Use serial data loading when opening this document"
Manual: "Forces this specific analysis to load data from multiple data sources in a sequence after each other when the document is opened."

This is a compatibility setting for documents that expect the old behavior rather than the parallel loading on multiple threads that was introduced in version 11.4.
If true, parallel data data loading is not used for this document.
If false, parallel data loading may be used.

• https://docs.tibco.com/pub/sfire-analyst/11.4.0/doc/html/en-US/TIB_sfire-analyst_UsersGuide/other/other_details_on_compatibility_setting.htm