. Master tape (operational program, maintenance
program, or data file)
Blank tapes, cartridges, or cassettes, and those tapes
with data that may be written over are referred to as
scratch tapes. Those tapes that contain programs or
data that is to be saved and protected are known as
master tapes. You must ensure that master tapes being
mounted on or in a unit are protected against a write
operation.
The write protection sensors of the tape unit check
the mounted tape for a ring, switch, or tab to determine
if the contents of the tape are to be protected from a write
operation. The write protection circuitry prevents the
computer from inadvertently writing over
write-protected programs or data.
To prevent the inadvertent destruction of a master
tape through operator error or equipment malfunction,
you should copy master tapes of programs onto
working copies.
Two working copies should be
maintained for each master program in current use.
Only use the master tape to generate new
working copies. The working copies can then be used
for repeated operations, such as program loading, that
will eventually wear down the recording surface of the
tape. Use of a master tape as a working copy increases
the potential of damage to the tape and loss of data or
programs beyond recovery. Upon receipt of new master
tapes, the old master tape copies should not be destroyed
until the new master tape has proved reliable.
IDENTIFYING AND CORRECTING
PROBLEMS WITH MAGNETIC TAPES.—
Magnetic tapes used in a system tend to develop a
variety of problems. These problems fall into three
basic categories:
l Data loss
l Compatibility problems
Q Winding errors
Data Loss.— Data written on magnetic tape maybe
lost for a variety of reasons. Tapes that are broken,
wrinkled, stretched, or are worn, with the oxide flaking
off, will not retain data. Excessive heat or cold, or the
shock to a tape that is dropped can affect the stored data
by rearranging the magnetic flux patterns. Data maybe
lost or misread because of accumulations of magnetic
oxide particles built up on tape transport read/write
heads and mechanics.
When you encounter magnetic tape read or write
errors, follow these simple steps:
l
l
l
l
Remove the tape from the unit and clean the
transport
If errors persist, attempt to load/write the tape on
a different transport
If the tape is a working copy, make a new
working copy by recopying the master to anew
tape
If the tape has visible damage, or if errors follow
the tape to different transports, submit the tape
for stripping or cleaning/certifying
Compatibility Problems.— Tapes that can be read
from one transport and not from another of the same
system indicate a problem in the alignment of the
system’s tape transports. In other words, the transports
are incompatible. All tape transports of the same type
in a system, or out of any other system, should be
compatible. Compatible means that all tapes written
on a transport can be read without errors by all other
transports of the same type and that a transport can read,
without errors, all tapes written by other transports of
the same type.
Align tape transports to the mechanical and
electrical specifications of the manufacturer to ensure
compatibility within system transports and the same
type transports in other systems.
Winding Errors.— Winding errors are another
cause of tape failure.
They happen when improper
winding practices create excessive or uneven force as
the tape is being wound onto a tape reel. The form taken
by the tape after it is wound onto a reel is called the tape
pack. Winding errors can cause a deformed tape pack
that will prevent good head-to-tape contact.
In most cases, a deformed tape pack can be
corrected simply by rewinding it onto another reel at the
proper tension and the right temperature and humidity.
The four most common winding errors are cinching,
pack slip, spoking, and windowing.
s Cinching— Cinching happens when a tape reel
is stopped too quickly. The sudden stop causes the outer
layers of tape to keep spinning after the inner layers have
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