16.10 - Checkpoint/Restart - Access Module

Teradata Tools and Utilities Access Module Programmer Guide

prodname
Access Module
vrm_release
16.10
created_date
May 2017
category
Programming Reference
featnum
B035-2424-057K

The Teradata Database checkpoint/restart feature must be supported by customized Access Modules whenever possible.

  • Checkpoints are supported by the File Get Position calls that specify Reqtype pmiPIDMOptGetPos.
  • Restarts are supported by File Set Position calls that specify Reqtype pmiPIDMOptSetPos.

If an Access Module cannot support checkpoints and restarts, a pmrcUnsupported return code needs to be returned for all calls when Reqtype is either pmiPIDMOptGetPos or pmiPIDOptSetPos.

The contents of the buffer returned in response to a File Get Position call depends on the Access Module. However, the contents must configure the Access Module so that the next File Read function (Reqtype pmiPIDMOptRead) returns the same data block that is returned prior to the File Get position call. If a restart is attempted, the same data must be returned to the Access Module from the File Set Position function request.

The buffer is maintained by the client in the job-specific checkpoint information.

For example, assume that three record blocks were read by an Access Module prior to receiving a File Get Position call, and that record block #3was the last block returned. If that reading continued, and then a File Set Position function was received, the information provided is that which was previously returned by the Access Module in the previous File GetPosition function call. The Access Module reconfigures its internal state so that the next record block returned by the next File Read function call is record block #3.