TDP commands can be issued from TDPPARM during initialization, from operator consoles (or programs that simulate consoles), for z/OS and VOS3 from the Subsystem Interface or the system MODIFY command, by the Teradata DBCCMD application, or from CLIv2 applications using the DBCHCL Command function. When issued from a z/OS or VOS3 console, responses are returned to that console (on z/OS, both one and four byte console ids are supported).
Just as all work for TDP, commands require TDP cells for processing. A shortage of XMS cells will force TDP to convert a command issued from the Subsystem Interface to the system MODIFY command. If such a shortage prevents command processing, the system MODIFY command can be used to issue TDP commands. A shortage of non-XMS cells can prevent all TDP command processing or the responses to command. A shortage of any cell type will have previously generated a message as described in the Messages Having Operational Impact section of TDP Messages. Since command processing can be affected, such shortages should be dealt with as they occur.