SPI Common Extensions Manual

Glossary
SPI Common Extensions Manual—427508-001
Glossary-11
snapshot file
snapshot file. A file used by context-sensitive servers to record response data for a
command. It is used to ensure a consistent response in cases where data—for
instance, statistics—might change between one reply message and the next. Compaq
subsystems do not use snapshot files, but subsystems you write can do so.
special operation. An operation, such as a control operation or an operation that gets
information from the buffer (rather than the header), performed by the SSGET or the
SSPUT procedure. Special operations include obtaining the length or number of
occurrences of a token, changing the current position, clearing the last-error
information, or deleting a token from the buffer. A program directs SSGET or SSPUT to
perform a special operation by passing to the procedure one of a set of special SPI
token codes. These special token codes do not represent tokens in the buffer, but
simply direct SSGET or SSPUT to perform the indicated operations.
SPI. See Subsystem Programmatic Interface (SPI).
SPI buffer. A block of memory where the SPI procedures create and manipulate SPI
messages.
SPI definitions. See SPI standard definitions.
SPI error number. A number that indicates whether a call to an SPI procedure completed
successfully and why it failed if it did. This number is returned in the status parameter
on calls to the SPI procedures. The SPI error number does not reflect the success or
failure of a command. It applies only to errors in the building and decoding of a
message in an SPI buffer.
SPI message. A message specially formatted by the SPI procedures for communication
between a management application and a subsystem or between one subsystem and
another. An SPI message consists of a collection of tokens. To retrieve a token from
the message, the application passes a token code to SPI, which scans for the
appropriate token and returns its value to the application. An SPI message is a single
block of information sent at one time as one interprocess message. The two types of
SPI messages, distinguished by SPI message header type are command and
response messages and event messages. See header type.
SPI message header. The initial part of an SPI message. The first word of this header
always contains the value -28. The remainder of the header contains descriptive
information about the SPI message, most of which is accessible as header tokens. The
tokens in an SPI message header differ according to the header type. The header of a
message that contains a command or response differs somewhat from the header of
an event message. An application can use SSGET or EMSGET calls to retrieve the
values of header tokens and can use SSPUT calls to change the values of some.
However, there are certain basic differences between header tokens and other tokens.
See header token.