Abstract: 1. A cyclic compound of the formula (I) or a pharmacologically acceptable salt thereof, wherein X is ?CH— or ?N—, Y is —NH—, —NR4—, —S—, —O—, —CH?N—, —N?CH—, —N?N—, —CH?CH—, etc., R1 is a lower alkoxy group, an amino group, a heterocyclic ring containing N atom(s), or a hydroxy group substituted by a heterocyclic ring containing N atom(s) (each of which is optionally substituted), R2 is a lower alkylamino group which is optionally substituted by an aryl group, a lower alkoxy group which is optionally substituted by an aryl group, a lower alkoxy group substituted by an aromatic heterocyclic ring containing N atom(s), R3 is an aryl group, a heterocyclic ring containing N atom(s), a lower alkyl group, a lower alkoxy group, a cyclo lower alkoxy group, a hydroxy group substituted by a heterocyclic ring containing N atom(s), or an amino group (each of which is optionally substituted), and R3 and a substituent in Y may be combined to form a lactone ring.

Abstract: A servo system for use in a magnetic disk apparatus has a memory unit prestoring offset data used to correct offset which can occur when a head is moved to a target track on the disk. The CPU of the servo system uses the offset data stored in the memory unit when the head is moved to the target track at the time of reading and writing data. A settling time period is obtained while the head is moved to the target track on the disk at the time of data reading/writing. The difference between the settling time period is compared with a reference value. If the difference does not fall within an allowable range, the offset data stored in the memory unit is renewed.