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PE - Parsing Engine


PE, acronym for "Parsing Engine," is the type of vproc (Virtual Processor) for session control, task dispatching and SQL parsing in the multi-tasking and possibly parallel-processing environment of the Teradata Database.


DEFINITION

PE, acronym for "Parsing Engine," is the type of vproc (Virtual Processor) for session control, task dispatching and SQL parsing in the multi-tasking and possibly parallel-processing environment of the Teradata Database. Vproc is a software process running in an SMP (Symmetric Multiprocessing) environment or a node.


COMPONENTS

The components of a PE vproc can be classified as the following:

   1. Parser: It desolves SQL statements into RDBMS processing steps;
   2. Query Optimizer: It decides the optimal way to access data;
   3. Step Generator: It 1) produces processing steps, and 2) encapsulates them into packages;
   4. Dispatcher: It 1) transmits the encapsulated steps from the parser to the pertinent AMPs, and 2) performs monitoring and error-handling functionalities during step processing;
   5. Session Controller: It 1) manipulates session-control activities (e.g., logon, authentication, and logoff), and 2) restores sessions after client or server failures.


OVERVIEW

PE is an instance of the database management software responsible for the communication between the requesting client and the relevant AMPs, usually via the BYNET. Each PE runs independently to handle sessions, parse SQL statements into processing steps with optimization, dispatching the steps to the relevant AMPs and sends the processing results back to the requesting client.

The PE vproc was invented in Teradata V2 to replace the following dedicated physical processors that performed the similar functions on the DBC 1012 systems:

    * The InterFace Processor(IFP) - The IFP was responsible for the communication between the DBC and the HOST. Its components included parser, dispatcher, session controller, client interface and YNET interface.
    * The COmmunication Processor (COP) - The COP was similar in function as IFP, but responsible for communication with network-attached hosts (DOS-PC/UNIX).

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