Spool request &1 in system &2 is write-protected

What causes this issue?

The selected spool request is currently being written to and therefore
cannot be deleted.

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?

Try again later.
Note: If you are unable to delete the spool request after waiting a
long time, a transaction may have terminated and the write lock was not
deleted (status "+" in the spool request overview). Notify your system
administrator.

Procedure for System Administrators

Wait at least an hour (or longer if long running background processes
are running). Then call the consistency check in spool administration
to delete any old write locks.

Error message extract from SAP system. Copyright SAP SE.