Request Processing

VPROC Operations

VPROC operations are generally either one of two different types.  Either a VPROC request is a single VPROC request or an all VPROC request.  Once the request reaches the Parsing Engine (PE), the PE determines (by a row hash) which VPROC or VPROCs contain the requested data. 

A single VPROC request is one in which Teradata uses the Row Hash to determine which VPROC contains the requested rows.  An example of a single VPROC request is a Primary Index retrieveal.  In the SQL example below, since the contact_number is known before hand the PE can go directly to the DSU that contains the requested data.

An all VPROC request is more complex than the single VPROC request, but the component parts of the request are the same.  An example of an all VPROC request would be a request where the WHERE statement contains a range of values or all values above or below a given values.  In the example below, the PE is forced to search all DSUs for the rows that meet the range criteria of contact_number set in the SQL statement.