position the control circuit 110 could briefly move the head away from the park position in order to write and read test data to and from the reserved track 28 and could then calculate the ser based on this test data in fig2 if the detected soft error rate ser is found to be below the threshold at block 162 the control circuit 110 essentially shuts down system operation at block 163 alternatively however the control circuit 110 could take some other course of action for example the control circuit 110 could 1 prevent a user from writing data 2 allow a user to write data only in a write with verify mode or 3 initiate recovery activities such as head cleaning in order to improve the error rate performance in blocks 161 163 of fig2 an error condition is generated after checking the soft error rate ser at just one radius of the disk which is the radius associated with track 28 alternatively however when the ser is found to be below the threshold at any radius the ser could be checked again at a different radius and then the error condition would be generated only if the ser was found to be below the threshold at each such radius a further consideration relates to the fact that the blocks 161 and 162 involve evaluation of the soft error rate ser it would alternatively be possible to check for.