Two Response Buffers - Call-Level Interface Version 2

Teradata Call-Level Interface Version 2 Reference for Workstation-Attached Systems

Product
Call-Level Interface Version 2
Release Number
15.10
Language
English (United States)
Last Update
2018-10-07
dita:id
B035-2418
lifecycle
previous
Product Category
Teradata Tools and Utilities

Two Response Buffers

Usage Notes

The Two Response Buffers field specifies whether or not double-buffering is to be used for the response.

 

Language

Variable Name

COBOL:

DBCAREA-TWO-RESP-BUFS

C: DBCAREA.H:

two_resp_bufs

 

Routine

Action Taken

DBCHINI:

writes

DBCHCL:

reads (CON; RSUP: IRQ)

 

Used by

Action Taken

application program

writes

Two Response Buffers is initialized by DBCHINI to the default value provided for Two Response Buffers in the site’s SPB.

If the value provided is not appropriate for the application, before calling DBCHCL for the Connect, Run Startup, or Initiate Request function, the application program may set:

  • Change Options to Y, and
  • Two Response Buffers to:
  • Y, if the response is to be double-buffered.
  • N, if a single buffer is to be used for the response.
  • Double buffering is useful when large responses are expected from the Teradata Database and large response buffers are used. Substantial improvements in response time can result by transferring the next buffer-full of response data from the Teradata Database while the previous buffer-full is being accessed by the application program.

    The response buffer or buffers are re-stocked automatically by DBCHCL. The application program may have to wait for data to arrive if the application program is consuming the data faster than the Teradata Database can re-stock the buffer, but it does not have to arrange for data to arrive.

    Note: The connect request’s response is not double-buffered, even if Two Response Buffers is set to Y when DBCHCL is called for the Connect function. However, any other request’s responses on that session are double buffered, unless the setting of Two Response Buffers is changed before the request is submitted.

    Although the value of Two Response Buffers is read and stored by the Connect function, it is not used for the connect operation itself.

    Two Response buffers will be ignored if the fetch request is for LOB or cursor repositioning responses.