Write to the messages.log file, the operator messages log.
InterSystems IRIS® reports general messages, system errors, certain operating system errors, and network errors through an operator console facility. On Windows, there is no operator console as such and all console messages are sent to the messages.log file in the InterSystems IRIS system manager directory (install-dir/mgr). For InterSystems IRIS systems on UNIX® platforms, you can send operator console messages to the messages.log file or the console terminal.
For more information, see Monitoring Log Files.
The directory location of this file is configurable in the CPF file; see ConsoleFile.
The special variable $SYSTEM is bound to the %SYSTEM package. This means that instead of ##class(%SYSTEM.class).method(), you can use $SYSTEM.class.method().