15.10 - Unusable CP or NP - Call-Level Interface Version 2

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

Call-Level Interface Version 2
Programming Reference

A Channel Processor (CP) is a communication path using the mainframe channel between TDP and the Teradata Database; a Network Processor (NP) is a communication path using the network between TDP and the Teradata Database. Since more than one CP or NP is often installed, the failure of one does not prevent communication with the Database, but it does have a dramatic impact on requests that are using the failed CP or NP. Unlike a Database restart in which all requests are terminated, leaving the sessions in a known, usable state, the failure of a CP or NP does not cleanup current requests but since their state cannot be ascertained by TDP, TDP must logoff the affected sessions. A return code of 544 indicates this condition. If the application is to recover it must connect that session again, ascertain whether the requests successfully completed, and continue processing as appropriate. However, the return code is presented immediately but it may take an indeterminate amount of time for TDP to abort the original request and logoff the original session, so any Database resources associated with that request and session may not yet have been freed so may not yet be available.