SPI Common Extensions Manual

SPI Common Extensions Manual—427508-001

Glossary-1

Glossary

attribute. A characteristic of an object. For example, two attributes of a DNS alias are an

alias type and domain. Two attributes of a communications line might be its baud rate

and its retry count. In SPI messages, an attribute of an object is usually expressed as a

simple token or a field within an extensible structured token. Tokens themselves have

attributes: length, count, address, and offset. Programs can retrieve attributes through

special SSGET operations.

buffer. A block of memory for temporary storage of data that is being moved from one

location to another. For instance, data to be sent in an interprocess message is

encoded in a buffer. The file system copies the contents of this buffer to another buffer

within the memory space of the recipient process. See also message buffer and SPI

buffer.

built-in. A Compaq Tandem Advanced Command Language (TACL) primitive function or

variable. Names of built-ins begin with a pound sign (#). TACL provides the #SSGET,

#SSGETV, #SSINIT, #SSMOVE, #SSNULL, #SSPUT, and #SSPUTV built-ins for

working with SPI messages.

command. A request for action by or information from a subsystem, or the operation

demanded by an operator or application. A command is typically conveyed as an

interprocess message from an application to a subsystem.

command message. An SPI message, containing a command number and related tokens,

that a requester sends to a subsystem manager process. See SPI message.

command number. A number that represents a particular command to a subsystem. Each

subsystem with a token-oriented programmatic interface can have its own set of

command numbers, which are represented in Data Definition Language (DDL) by

constants with names of the form subsys-CMD-name, and in programs by TAL literals

or defines, COBOL level-01 variables, or TACL text variables. The command number is

stored in the SPI message header.

compatibility. The ability of two or more elements in a system to work together correctly.