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Rotational Delay
Rotational delay is the time required for the desired
record area to reach the read/write head so that data
transfer can begin. This time can range from zero to
almost a full revolution. Half a revolution (average
rotational delay) is generally used for timing purposes.
The maximum and average rotational delays for
3340 / 3344 drives are:
Maximum rotational delay : 20.24 milliseconds
Average rotational delay : 10.12 milliseconds
Note: Use of the Rotational Position Sensing
featire
minimizes the effect of rotational delay by
permitting the drive to disconnect from the channel,
thereby allowing use of other drives during a
latency period.
Data Transfer
Nominal read/write rates for the disk drives are:
Bytes-per-second : 885,000
Microseconds-per-byte
= 1.13
DATA SECURITY AND PRIVACY
The 3340 and 3344 have a Read Only function. This
function, in conjunction with previous methods such as
File Protect and Seek Verification, offer a means of
limiting access to data areas of the data module.
Read Only Function
3340 MODELS
The Read Only function provides the means for
protecting designated data modules from being
rewritten or erased.
Each data module is equipped with an inset in the
handle. The operator can change the inset position
before inserting the data module in the drive.
Note: Iftis insert is only accessible when the data
module is not on the drive (see the "Operating
Instructions" sect ion).
When the Read Only option is made, any Write
command addressed to the drive is rejected. Subse-
quent sense Lnformation indicates Command Reject
(byte 0, bit 0) and Write Protect (byte 1, bit 6).
3 3 4 4 M O D E L S
In the 3344 dual-drive models, the Read Only func-
tion is controlled by a switch on the operator panel
for each drive.
File Protection
Control of Write and Seek commands within a pro-
gram can be affected by the Set File Mask command.
A description of the Set File Mask command is given
in the ISC and 3830-2 reference manuals.
By entering a Set File Mask, selected Write and Seek
commands can be inhibited even though they appear in
the command chain.
Seek Verification
The 334O/3344 track format includes two bytes in
each count area and home address (physical address,
PA) for seek verification. When a count area or home
address is processed during Read, Search, or Clock
operations, the bytes are compared with the most
recent seek address. A non-compare results in termi-
nation of the operation at the end of the count area or
home address with channel end, device end, and unit
check. Seek check is also indicated in the sense
information.
Input/OutputOperations 17
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