InterSystems FAQ rubric
If you restart the OS after changing the machine name without stopping InterSystems IRIS (hereinafter referred to as IRIS), a problem occurs when IRIS cannot start.
To get started, delete the <installation directory>\mgr\iris.ids file.
iris.ids file stores the started node name and shared memory information (shared memory ID). It is created when IRIS starts and deleted when stopped (iris stop or iris force). If you stop (restart) the OS without stopping IRIS, iris.ids, which contains IRIS startup information, may remain.
IRIS checks iris.ids during the next startup

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