InterSystems IRIS Data Platform 2019.2  /  ObjectScript Reference

ObjectScript Reference
Structured System Variables
Previous section          
InterSystems: The power behind what matters   

A structured system variable name, or SSVN, is a nonscalar system variable that is organized like a global variable. SSVNs allow you to write portable programs that can retrieve information about system data. The same ObjectScript code can retrieve system data information from any InterSystems IRIS implementation using structured system variables.
Each SSVN has a structure where subscript values are any of the following:
You provide information about entities by providing values for subscripts which are identifiers and for attribute nodes.
SSVNs use the caret and dollar sign (^$) as a standard prefix followed by:
  1. An optional (extended syntax ) specification of the namespace about which you want information
  2. One of a designated list of names.
You then follow the name with one or more expressions in parentheses. These expressions are called subscripts. The syntax is as follows:
^$[|namespace|] ssvn_name(expression)
Generally, you cannot use SET and KILL commands for structured system variables because they do not necessarily have data values. The information that structured system variables provide is often the existence of specific subscript values. In most cases, you can use the $DATA, the $ORDER, and the $QUERY functions to examine subscript values.
InterSystems IRIS supports the following structured system variables:
The meaning of each of these SSVNs and use of their subscripts is explained in the following sections.
Each description identifies which functions are allowed with the particular structured system variable. Each description contains one or more examples about how to use structured system variable as arguments to the $DATA, $ORDER, and $QUERY functions to scan system table information.

— ^ —

Previous section          
Send us comments on this page
View this book as PDF   |  Download all PDFs
Copyright © 1997-2019 InterSystems Corporation, Cambridge, MA
Content Date/Time: 2019-08-16 05:50:13