Abstract: The present invention provides two methods, apparatus, and computer instructions for controlling tape movement in a tape drive system. In the first method, the direction of tape movement is determined with respect to a file reel and a machine reel. If the direction of tape movement is toward the file reel, the tape is moved using machine reel control, and if the direction of tape movement is toward the machine reel, the tape is moved using file reel control. In the second method, the size of a file reel, designated as the file radius, and the size of a machine reel, designated as the machine radius, are determined. If the machine radius is smaller than the file radius, tape motion is carried out using machine reel control, and if the file radius is equal to or smaller than the machine radius, tape motion is carried out using file reel control.

Abstract: Track positioning of a scanning tape head in a helical tape system may be adversely affected by relative offsets between elements in read element pairs and in write element pairs accessing synchronization patterns. Compensating for variations in the position of read and write elements accessing a given pair of data channels is accomplished by using the relative offset of the first detected synchronization patterns in each pair of data channels as a measure of the relative locations of write elements producing the synchronization patterns and read elements accessing the synchronization patterns. This relative offset is then used to correct subsequent synchronization pattern readings taken from the data channel pair.

Abstract: A method and system for controlling position of a tape head relative to a tape includes sensing the servo track of a tape with servo read elements of the tape head. A position error signal is then generated for each servo read element. indicative of a position of the servo read element relative to the servo track. The position error signal from each servo read element is then determined to be either an unexpected or an expected position error signal. A position error signal is unexpected when at least one measured parameter based on a function of movement of the position of the servo read element relative to the servo track is greater than a predetermined threshold limit and is expected when the at least one measured parameter is lesser than the predetermined threshold limit.

Abstract: Tape drives and methods for reading/writing on first and second surfaces of a tape include a pair of read/write heads for reading/writing on the surfaces at the same time in synchronism as the tape moves across the heads. A controller determines if the heads are reading corresponding portions of the surfaces of the tape at the same time. The controller also determines if the heads are moving to corresponding portions of the surfaces of the tape in the same time period. The controller further determines if the heads are moving to corresponding tracks on the surfaces of the tape at the same time.