SPI Programming Manual (G06.24+, H06.03+, J06.03+)

Glossary
SPI Programming Manual—427506-006
Glossary-5
header token
header token. A special token, present in every SPI message, that provides information
about the message as a whole. The header tokens are typically items common to all or
most messages of a specific kind. Header tokens differ from other tokens in several
ways: they exist in the buffer at initialization and their values are usually set by SSINIT,
they can occur only once in a buffer, they are never enclosed in a list, they cannot be
moved to another buffer with SSMOVE, and programs cannot position to them or
retrieve their values using the NEXTCODE or NEXTTOKEN operation. Programs
retrieve the values of header tokens by passing appropriate token codes to SSGET,
and can change the values of some header tokens by passing their token codes to
SSPUT. Examples of header tokens for commands are the command, the object type,
the maximum-response token, the server-version token, the maximum-field-version
token, and the checksum token. Examples of header tokens for event messages are
the event number, the event generation time, the logging time, the maximum-field-
version token, and the checksum token.
header type. A header token in an SPI message that indicates whether the message is a
command or response message or an event message.
information command. A command that retrieves information about an object but does not
act on the object or change it in any way. Extended SPI classifies informational
commands as nonsensitive for security purposes. Compare with command
.
initial position. In an SPI buffer, the location just prior to the first token that is not a header
token. Compare with current-token position
and next-token position.
initialize. To prepare a data structure to have values assigned to it. For example, the SPI
SSINIT procedure initializes the buffer by building the message header; the SSNULL
procedure initializes an extensible structured token by assigning null values to the
fields of the structure.
is-present field. A field in a structure that indicates whether the value in a related field was
supplied by the program that sent the structure. In most cases, a field to which the
program made no assignment has the null value that was set by SSNULL. A
subsystem defines a separate is-present field when no null value can be defined that is
not a valid value for the field.
list. In an SPI message, a group of tokens that defines a context for scanning the buffer
and extracting tokens with the SSGET procedure. A list imposes a hierarchy on the
buffer. To retrieve tokens from a list, a program must first enter the list by retrieving the
initial list token, then retrieve tokens from the list, and then exit the list to the next
higher level of tokens by retrieving the end-list token. SPI defines four kinds of lists:
data lists, error lists, segment lists, and generic lists.
list token. A token that marks the beginning of a list in an SPI message. The four list
tokens, each marking one of the four types of SPI lists are: ZSPI-TKN-DATALIST for
data lists, ZSPI-TKN-ERRLIST for error lists, ZSPI-TKN-SEGLIST for segment lists,
and ZSPI-TKN-LIST for generic lists. Compare with end-list token
; see also syntax
token.