New command buffer

The new command buffer allows an initialization exit to change the command that a user issues. Figure 1 shows the format of the command buffer.

To change the command buffer, the exit must:

Obtain storage for a new command buffer
Build the new command buffer. When you build the new command buffer, make sure the 4-byte header of the command buffer contains the correct length and offset values.
Update the key, length, and data fields in the parameter list for the new command buffer as follows:
Key

X'02'

Length

the length of the new command buffer

Data

the address of the new command buffer

If the exit returns a new command buffer, the command processor uses the new command buffer for the remainder of its processing. The command processor passes the new command buffer to all subsequent exits that it invokes.

You must also provide a termination exit to free the storage that the initialization exit obtained for the new command buffer.