SAP Message 5A198 - Personnel number & is locked

Diagnosis
You are editing an object in a structure which contains the specifiedpersonnel number. To continue the transaction, you must lock thepersonnel number.
However, it has already been locked elsewhere, so that you have no moreaccess to this personnel number. You must discontinue your transaction.

Procedure
Check to make sure that you, yourself are not blocking the number in analternative mode.