
Overview of SPI and EMS
Using Programmatic Interfaces
107365 Tandem Computers Incorporated
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The buffer transports the tokens to and from the target subsystem. The following is a
simplified diagram of an SPI message. Again, each token contains a token code and a
token value:
• • •
Header
Token
Token
Token
SSID
Command #
Obj-Type #
and so on
Data Portion
• • •
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The ZSPI-TKN-COMMAND code and others listed previously are defined in files
provided by Tandem (stored in ZSPIDEF and ZSPISEGF subvolumes). When you use
SPI or EMS, you include definition files for the language you are using and subsystem-
specific definition files for each subsystem you want to manage. To retrieve event
messages, you also need the EMS definition file for the subsystem.
TACL provides built-in functions that initialize and manipulate the contents of
message buffers. To establish communication with a subsystem, you use
#REQUESTER or #SERVER with IN set to $RECEIVE to establish communication and
#APPEND(V) and #EXTRACT(V) to send and receive a buffer, respectively.
SPI and EMS are based on the same message format, but the two interfaces differ in
their purposes and uses; used together, they can provide a wide range of management
services. For example, you can use EMS to monitor a large array of subsystems. If a
significant situation arises, you can use SPI to initiate a dialog with the appropriate
subsystem. You can also use TACL to learn about SPI and EMS interactively.