SPI Common Extensions Manual

Subsystem Control Point

SPI Common Extensions Manual—427508-001

3-6

Opening an SCP Process

To send SPI commands to an SCP process, the process must be opened using the

#ZSPI qualifier. That is, the SCP process name must be specified as $process-

name.#ZSPI. For example, if the SCP process name is $ZNET, your application opens

it as $ZNET.#ZSPI. The #ZSPI qualifier indicates to the SCP process that subsequent

messages from this process follow the SPI protocol.

The $ZNET SCP Process

The Subsystem Control Facility (SCF) is an interactive subsystem management

application that converts typed commands into SPI command messages and routes

them through an SCP process to the target subsystem. Unless otherwise directed,

SCF uses an SCP process named $ZNET, and an SCP process with this name can be

found running on most nodes as a result of SCF activity. Management applications

other than SCF can route commands through the $ZNET process to avoid having to

start other SCP processes.

Sending Commands and Retrieving Responses

Management applications prepare SPI buffers by using the standard SPI procedures.

After opening an SCP process for SPI-formatted messages, the applications use the

WRITEREAD procedure to send the command buffers and retrieve the corresponding

responses. For a description of this process, see the

SPI Programming Manual

Note. Do not confuse the open here with the open used to send the startup message to the

SCP process. The open described here is for using the SPI interface to exchange messages.

The other is only for sending a startup message to a newly created SCP process. After the

startup message is acknowledged, the initial SCP process open must be closed, and the

process reopened for management as described here.