Cleaning and Recertifying Magnetic Tape

CLEANING AND RECERTIFYING MAGNETIC TAPE How important is tape cleaning and recertification? Let us answer that question by asking another question: When do you suppose tape failures are most likely to occur? If you answered, when the tape is being used on the computer system; then you are correct. Consider this example: an unrecoverable tape error appears while the operator is trying to read in reel four of an eight-reel master file; the operator is about 3 hours into a very important job, and finds out there is no way to recover (restart) the job starting with reel three of the input. A failure at this stage of the operation gets the operator and a good many other people very upset, for we all know that reruns are costly in both time and money. Such failures can be avoided if tapes are cleaned and recertified on a regular basis. It is well worth the effort to properly care for tapes according to a regular planned schedule; since this avoids upset and inconvenience and gives your users confidence that your AIS facility is running smoothly. Careful and planned maintenance of magnetic tapes can minimize and even possibly eliminate a lot of lost computer time. The first step in every magnetic tape maintenance program is, obviously, careful cleaning. Despite the many safeguards against contamination, you can believe that magnetic tape will eventually acquire some contamination and cause read or write errors. You will find the greatest number of tape errors normally occur in the first 100 feet of a reel. When this is the case, the appropriate action is to cut off the contaminated area, relocate the BOT reflective marker, and continue to use the tape (see figure 2-11). In most cases, the reduced length will not detract from its usefulness. This procedure is known as stripping a tape. After a tape has been stripped five times, it should be reloaded (transferred) onto what we call a mini-reel. A mini-reel is about half the size of a standard reel of tape. If the errors continue throughout the length of the tape, you should determine whether the errors are distortion errors or dirt errors. Distortion errors are usually the result of careless handling (abuse) of the tape and can rarely be corrected. Distortion errors can be seen as wrinkles, creases, turned-up edges, or a slight stretching of the tape. Dirt errors usually result from the accumulation of microscopic foreign matter on the tape surface and can be removed by careful cleaning. To do this, you need to use a tape cleaner. Tape cleaning is the process of removing all foreign particles (known as residual buildup) and protruding debris from the oxide and back side (the shiny side) of the tape. This process does not destroy any of the data that has been previously recorded on the tape. New tape has a tendency to shed oxide particles near the surface for approximately the first six passes through the read/write heads of the magnetic tape unit. Unless the new tape is cleaned at least twice, increased tape unit head wear could result. You will also find that deterioration of the edges of the tape is the major cause of most tape-generated debris. Edge guides that help to direct the tape along the tape path also cause a constant edge-scuffing. This results in a further breakdown of the oxide/base layer interface of the tape. An effective Figure 2-11.—A 100 feet of contaminated tape being removed from reel (stripping). 2-17