I'm not sure I understand your query. What exactly do you mean by "Security Type" ? Is this for an input or an output of an extraction request ? Which one ? And is your query related to a particular asset class ?
I shall attempt to answer several possible cases, hopefully one applies to your query:
To identify an instrument in a query we use the Identifier Type. 41 are supported: RIC, Cusip, ISIN, etc. These can be sen in the API Reference Tree: in that screen set IdentifierList to InstrumentIdentifiersList, then click on the drop down in the IdentifierType line:
For data output fields we have several that could potentially correspond to what you are searching for:
These fields have equivalent ones that give a textual description, "Asset Type Description", "Asset SubType Description", "Debt Type Description", "Government Bond Type Code Description" and "Instrument Type Code Description"
This list is not exhaustive, to find them all see the Datascope Data Content Guide, tab "Field Descriptions". All field names are in column D, their description is in column E. Column C contains the corresponding extraction (report) type. Columns F and following give information on the format. Column I might be of interest to you as it gives links to lists of possible values (I added them to the field names above). Columns O and following tell you what asset classes are covered.
Does this help ?
Within DSS product, Report Type will help you to identify the correct request to use.
If this is what you are looking for, the information is in Datascope Data Content Guide, tab "Report Types".
Several report templates carry field "instrument type", which we can pinpoint by searching "Field Descriptions" within content guide for "instrument type".
To get further details on specific content, please contact Content Helpdesk and place an inquiry.