Enter a valid log mode

What causes this issue?

The program was terminated because an invalid value was entered for
the log mode. Possible values are:
O = open log, C = close log, A = collect log records.

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?

Enter a valid log mode.

Error message extract from SAP system. Copyright SAP SE.