17.10 - Asynchronous Connects - Call-Level Interface Version 2

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

Product
Call-Level Interface Version 2
Release Number
17.10
Release Date
October 2021
Content Type
Programming Reference
Publication ID
B035-2418-061K
Language
English (United States)

Asynchronous logons are available on all clients. For example, DBCHCL can be called more than once for DBFCON before calling DBCHCL for DBFFET.

As before, if Wait For Response is to be set to N for the fetch associated with the connect, the setting must take place at connect initiation time. Wait For Response is not read in at fetch time.

After a connect has been initiated, the application may do one of the following:
  • Call DBCHCL for DBFFET with Wait For Response set to Y, causing the DBCHCL to wait for the completion of an explicit session connect request.
  • Call DBCHWAT, which will return session identifiers for connect requests as they complete, and then call DBCHCL for DBFFET for the completed session.
  • Call DBCHCL for DBFFET repeatedly, with Wait For Response set to N, until the connect request has completed.

If the call to DBCHCL for DBFCON results in a non-zero return code, the connect has failed for the reason indicated by the value of the return code. However, the internal data structures are not de-allocated. The application program must de-allocate the CLI internal structures for the non-existing session by calling DBCHCL for DBFDSC. The Output Session Id from DBFCON is the appropriate value to place in Input Session Id for DBFDSC.

The database computer to be used is specified with the logon string. The set of services to be used is specified with the run string.

When DBCHCL returns control to the application program after initiating a connect operation, the initial status of the connect operation is reflected in the DBCAREA, including Output Session Id, Output Request Id. When DBCHCL returns control to the application program after the first fetch associated with the connect operation, the final status of the connect operation is reflected in the DBCAREA, including Output DBCpath, Output Host Id, and Output DBC Session Id.