How to write error log or audit log without orchestrator
We do have an activity called "Log Message"
which writes the specified diagnostic message at the specified level. These messages are also sent to Orchestrator and displayed in the Logs page.
The severity level of the message to be logged.
The following options are available: Trace, Info, Warn, Error and Fatal.
please refer the link to understand how to enable tracing .
The question is “How to write error log or audit log without orchestrator”, but your answer is using orchestrator.