SAPOSCOL not running (shared memory available)

What causes this issue?

Either there is no collector running and the shared memory is active, or
a collector has never run before so that no shared memory has been
created.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Run a collector before the SAP system is started. The collector from
Release 1.2A might run, but the system already has the status of 2.0A. A
new shared memory key is used for the new collector of Release 2.0A. The
new collector (status 2.0A) must be started.

Error message extract from SAP system. Copyright SAP SE.