15.10 - Use Presence Bits - Call-Level Interface Version 2

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

prodname
Call-Level Interface Version 2
vrm_release
15.10
category
Programming Reference
featnum
B035-2417-035K

Use Presence Bits is a one byte field that specifies the mode in which the client will package data to send to the Teradata Database.

 

In this language...

The variable name for Use Presence Bits is...

COBOL

DBCAREA‑USE‑PRESENCE‑BITS

PL/I

USE_PRESENCE_BITS

C

use_presence_bits

IBM Assembler

DBOIDTA

 

This routine...

Does this for Use Presence Bits...

DBCHINI

writes

DBCHCL

reads (CON; RSUP; IWPF; IRQ)

 

Use Presence Bits is used by...

To...

applications

write

Use Presence Bits is initialized by DBCHINI to the default value provided for Use Presence Bits in the HSHSPB.

When the value for Use Presence Bits is not appropriate for the application, you should perform the following procedure before calling DBCHCL for the following functions:

  • Connect
  • RunStartUp
  • Initiate with Protocol‑Function
  • Initiate Request
  • 1 Set Change Options to 'Y'.

    2 Change the value for Use Presence Bits as follows.

     

    If the data string has been prepared in this mode...

    Then change the value for Use Presence Bits to...

    indicator (IndicData)

    Y

    record

    N

    Use mnemonics for the codes. Mnemonics are provided in the language definition file for the DBCAREA.

    To send null data to the Teradata Database, set Use Presence Bits to 'Y' and provide a data string as described for the IndicData parcel.

    Note: Since DBCHCL does not parse the request string, it is the responsibility of the application to check whether the request string contains a USING row descriptor and to set Use Presence Bits, Using Data Pointer, and Using Data Length appropriately.

    See “Variable Length Request” on page 197, for the preparation of the input data string: the order of the two‑byte length field (if used), the bytes containing indicator bits (if used), and the bytes containing data values.

    Although Use Presence Bits is read during the call to DBCHCL for the Connect function and the RunStartUp function and is stored in the appropriate session and Request Control Blocks, it is not usually used by the functions. Neither function sends an input data string to the Teradata software, unless a macro that accepts the Use Presence Bits parameters is set up for the RunStartUp function.