Caché ObjectScript Reference - InterSystems Documentation

Structured System VariablesA structured system variable name, or SSVN, is a nonscalar system variable that is organizedlike a global variable. SSVNs allow you to write portable programs that can retrieve informationabout system data. The same Caché ObjectScript code can retrieve system data informationfrom any Caché implementation using structured system variables.Each SSVN has a structure where subscript values are any of the following:• Entity identifiers• Literals• Attribute keywords.You provide information about entities by providing values for subscripts which are identifiersand for attribute nodes.SSVNs use the circumflex and dollar sign (^$) as a standard prefix followed by:1. An optional (extended syntax ) specification of the namespace about which you wantinformation2. One of a designated list of names.You then follow the name with one or more expressions in parentheses. These expressionsare called subscripts. The syntax is as follows:^$[|namespace|] ssvn_name(expression)Generally, you cannot use SET and KILL commands for structured system variables becausethey do not necessarily have data values. The information that structured system variablesprovide is often the existence of specific subscript values. In most cases, you can use the$DATA, the $ORDER, and the $QUERY functions to examine subscript values.Caché supports the following structured system variables:• ^$GLOBAL• ^$JOB• ^$LOCK• ^$ROUTINECaché ObjectScript Reference 501