IBM 3340 User manual

GA26-1619-4
File No. S370-07
Systems Reference Manual for
IBM 3340/3344 Disk Storage
ht

PREFACE
This publication is intended to familiarize data proc-
essing personnel with the characteristics of IBM
3340/3344 Disk Storage. The reader should have
prior knowledge of direct-access storage devices and
concepts.
This publication is organized by topics as follows:
•INTRODUCTION —Describes basic units and
lists highlights and functions.
•CONFIGURATIONS and ATTACHMENTS —
Defines some possible combinations and system
attachments for the 3340/3344.
•FEATURES —Describes both standard and
optional features available for the 3340/3344 with
illustrations of some combinations.
•FORMATS —Describes and illustrates the record
and track formats for data. Also provided are
Record/Track capacity charts including formulas
for capacity calculations of various length records.
•INPUT/OUTPUT —Includes addressing
methods, access times, and identifies security and
privacy means. Lists and summarizes the
3340/3344 command set and sense byte formats.
Also includes an error condition table and the
associated error recovery actions.
•OPERATING INSTRUCTIONS —Describes all
switches and indicators associated with the
3340/3344 Operator and Power Panels. Provides
suggested instructions for data module unloading
and loading procedures and the Enable/Disable
Read Only Function.
The following publications are recommended for
detailed information concerning the subjects covered
in this manual:
•IBM System/370 Principles of Operation, Order
No. GA22-7000.
•IBM 3348 Data Module Handling Procedures,
Order No. GA26-1625.
•IBM 3340 Disk Storage Fixed Head Feature
Users Guide, Order No. GA26-1632.
•IBM Reference Manual for Integrated Storage
Control, Order No. GA26-1620.
•IBM Reference Manual for 3830 Model 2
Storage Control, Order No. GA26-1617.
•The Data Processing Glossary, Order No. GC20-
1699, defines terms related to direct-access storage
devices.
•The functional characteristics manual applicable to
the parent system. Order numbers for functional
characteristics manuals can be found in the IBM
System13 60 and System/370 Bibliography,
Order No. GA22-6822.
Fifth Edition (July 1975)
This publication replaces and makes Reference Manual for IBM 3340 Disk
Storage, Order No. GA26-1619-3, obsolete.
Significant changes or additions to the specifications contained in this publication
are continually being made. Before using this publication in connection with the
operation of IBM equipment, contact the local IBM Branch Office for revisions.
Copies of this and other IBM publications can be obtained through IBM Branch
Offices.
Aform for reader's comments is provided at the back of this publication. If the
form has been removed, send your comments to the address below.
This manual was prepared by the IBM General Products Division, Graphics and
Publishing, Department G26, San Jose, California 95193.
©Copyright International Business Machines Corporation 1973, 1974, 1975.
ii IBM 3340/44 Reference Manual

CONTENTS
Introduction
IBM 3340 Disk Storage
Data Module
Defect Skipping
IBM 3344-B2/B2F Disk Storage
IBM 3340/3344 Units
3340/3344 Storage Control and Features 3
Storage Control Devices 3
Special Features 3
String Switch 3
Rotational Position Sensing 3
Fixed Heads 3
Configurations 4
3340 Storage Without 3344 4
Model 115 (115 DDA) 4
Model 125 (125 DDA) 4
Model 135 (IFA) 4
Models 135, 145, 155-11, 158, 165-11,
and 168 (3830-2) Models 145, 158,
and 168 (ISC) 4
3340/3344 Configurations 4
Model 135 (IFA) 4
Models 135, 145, 155-H, 158, 165-11.
and 168 (3830-2) Models 145, 158,
and 168 (ISC) 4
IBM 3348 Data Module 6
Data Module Types 6
Data Module Initialization 6
Data Surface Format 6
Formats 8
Record Format 8
Count Area 8
Key Area 8
Data Area 8
Track Format 8
Home Address 8
Track Descriptor Record (RO) 8
Data Records 8
Track Capacity 9
Input/Output Operations 16
Device Selection and Addressing 16
Device Address 16
Seek Address 16
Access and Data Transfer Speed 16
Access Motion Time 16
Head Selection Time 16
Rotational Delay 17
Data Transfer 17
Data Security and Privacy 17
Read Only Function 17
File Protection 17
Seek Verification ]7
Error Recovery Procedure 18
Error Correction Function 18
Error Condition Table 18
Error Recovery Action 18
Construction of Restart CCWs 18
Channel Commands 25
Sense Commands 25
Control Commands 25
Read Commands 25
Write Commands 25
Search Commands 25
Sense Data 34
Sense Byte Summary 34
Sense Bytes 0-7 Summary 35
Formats 1, 4, and 5Message Summary 36
3340 Sense Byte Format 1Summary 37
3344 Sense Byte Format 1Summary 39
Sense Byte Format 4Summary 41
Sense Byte Format 5Summary 42
Sense Byte Format 6Summary 43
Operating Instructions 44
3340 Operator Panel 44
3344 Operator Panel 44
3340/3344 Power Panel 45
Machines Without String Switch Feature 45
Machines With String Switch Feature 45
Data Module Loading 46
Data Module Unloading 46
Read Only Function 47
Enable Read Only Function 47
Disable Read Only Function 47
Index 48
Contents iii

FIGURES
Figure 1. IBM 3340/3344 Disk Storage 2
Figure 2. IFA 3340/3344 Maximum Configuration 5
Figure 3. ISC or 3830-2 Maximum Configuration ..5
Figure 4. Data Surface Track Layout 7
Figure 5. Data Module Geometry 7
Figure 6. Record and Track Format 10
Figure 7. Track/Cylinder Capacities -No Keys ..12
Figure 8. Data Module Capacities -No Keys .... 13
Figure 9. Track/Cylinder Capacities -With Keys 14
Figure 10. Data Module Capacities -With Keys ..15
Figure 11. Error Condition Table 20
Figure 12. Recovery Action Table 21
Sense Commands 26
Control Commands 27
Read Commands 29
Write Commands 31
Search Commands 33
Sense Bytes 0-7 Summary 35
Formats 1, 4, and 5Message Summary 36
3340 Sense Byte 1Summary 37
3344 Sense Byte 1Summary 39
Format 4Summary 41
Format 5Summary 42
Format 6Summary 43
Operator Panel, 3340 and 3344 44
Power Panel, 3340/3344 45
Data Module Load/Unload 46
Read Only Function 47
iv IBM 3340/44 Reference Manual

INTRODUCTION
The IBM 3340 Disk Storage provides direct-
access storage for IBM System/370 Models 115, 125,
135, 145, 155-11, 158, 165-11, and 168. The 3340
consists of aModel A2, control with dual-drive disk
storage, and up to three attached dual (B2) or single
(Bl) drive units. The 3344 large-capacity, dual-drive
unit can be substituted for the 3340 B-type units
on IBM System/370 Models 135, 145, 155-11, 158,
165-II,and 168.
The 3340/3344 is amodular, high-speed, large-
capacity disk storage subsystem for data base, data
communication, or general purpose use.
IBM 3344-B2/B2F DISK STORAGE
The IBM 3344-B2/B2F dual-drive unit provides
increased capacity, lower-cost-per-byte, direct access
storage. Each 3344 drive stores four times the
quantity of data of a70-megabyte data module by
using fixed media. The 3344 dual drives can replace
the 3340 B-drives in a3340 string on IBM System/
370 Models 135, 145, 155-11, 158, 165-11, and 168.
The 3344-B2F contains fixed head storage.
Defect skipping, similiar to that used on the 3340,
is also used by the 3344-B2/B2F.
IBM 3340 DISK STORAGE
The IBM 3340 direct-access storage introduces two
technological advances: adata module and defect
skipping.
Data Module
The sealed data module cartridge contains storage
disks, drive spindle, read and write heads, and access
arms. The data module has several advantages over a
disk pack:
•The drive data storage capacity can be changed by
using adifferent data module.
•The heads, storage disks, and drive spindle are
sealed inside the data module. This avoids contam-
ination from outside sources and reduces preven-
tive maintenance.
•Reliability is improved as each head reads only the
data that it previously wrote.
Defect Skipping
Defect skipping allows data to be stored both ahead of
and following asurface defect. All of the recording
track can be used except for minute portions. Since
the heads no longer need be moved to an alternate
track, access time is saved.
Data module capacity is not changed by defect skip-
ping and the user is unaware of defects.
IBM 3340/3344 UNITS
The 3340/3344 disk storage is made up of amaximum
of four dual-drives. The input/output interface is a
3340 Model A2 containing two independent drives
and their control logic. Up to three additional
attached dual-drives are controlled by the A2 unit.
The 3340 Model Bcontains either one or two drive
mechanisms. The Model Bl contains asingle drive;
the Model B2 contains two drives. Each model
contains all necessary electronic and power supply
circuits for internal use, but data control and power
sequencing comes from the A2 unit.
The 3340 Models A2, B2, and Bl use the 3348 data
module as astorage medium.
The 3344 dual-drive models use fixed media storage
instead of adata module. The following characteris-
tics apply to both storage device types except that the
3344 storage capacity is 279.5 million bytes-per-drive
and start time is not significant because the storage is
not moved.
The 3340/3344 offers the following:
•Start time -less than 20 seconds
•Average access time -25 milliseconds
•Average rotational delay -10.12 milliseconds
•Nominal read/write rate -885,000 bytes-per
second
•Data module capacity -34,944,768 or 69,889,536
bytes
Introduction 1

3340-B1
3340-A2
IBM 3340-A2 (Control and Two Drives)
CONTROL
•Interprets and executes macro-orders from the
storage control
•Regulates the storage control and disk storage
interfaces
•Serializes and deserializes data
•Checks data integrity by error detection and error
correction analysis
•Furnishes status to the system
•Performs diagnostic evaluation of the 3340/3344
storage string
DRIVES
•Responds to commands from the 3340-A2
(controller)
•Houses, loads, filters, and drives a3348 data module
which has various capacities (Models 35, 70, and
70F)
•Positions access mechanism with voice-coil and
maintains track following with electronic servo
system
•Selects the head
•Reads or writes data
•Provides safety and servicing information for subsys-
tem and system evaluation
IBM 3340-B1 (One Drive), IBM 3340 B2(Two
Drives), and IBM 3344 (Two Drives)
•Responds to commands from the 3340-A2
(controller)
•Positions access mechanism with voice-coil and
maintains track following with electronic servo
system
•Selects head
•Reads and writes data
•Provides safety and servicing information for subsys-
tem and system evaluation
3340-B1 and 3340-B2: Houses, loads, filters, and
drives the 3348 data module(s) of various storage
capacities (Models 35, 70, and 70F).
3344-B2 and 3344-B2F: Houses, filters, and powers
two fixed media drives. Each 3344 drive is equivalent in
capacity and format to four logical 3348 Model 70
volumes, atotal of 279.5 million bytes of data.
Figure 1. IBM 3340/3344 Disk Storage
2IBM 3340/44 Reference Manual

3340/3344 STORAGE CONTROL AND FEATURES
STORAGE CONTROL DEVICES
The following storage control devices can accommo-
date 3340/3344 disk storage.
•3830 Model 2Storage Control.
•System/370 Models 158 and 168 Integrated
Storage Control (ISC).
•System/370 Model 145 ISC.
•System/370 Model 145 Storage Control Frame
3345 Models 3, 4, and 5.
•System/370 Model 135 Integrated File Attach-
ment (IFA).
SPECIAL FEATURES
The 3340 disk storage has four special features. The
Model A2 can be supplied with the string switch and
the remote switch. All 3340 models can be ordered
with Rotational Position Sensing and Fixed Head
Storage.
The 3344 disk storage has no special features, as
Rotational Position Sensing is standard. Fixed Head
Storage is available, but must be ordered by model.
The 3344 Model B2F contains fixed head storage and
the Model B2 does not.
String Switch
The string switch feature is installed on the 3340-A2
(controller). This feature permits the 3340 string to
be dynamically shared by two storage control devices.
The feature includes two interlocked Enable/Disable
switches allowing the string to be dedicated to either
storage control or accessible by each. Aremote
control switch permitting the switches to be activated
from a158 or 168 Multiprocessor is also available.
Rotational Position Sensing
The rotational position sensing (RPS) feature reduces
the channel connection time required to search for a
given record after the track and head have been
selected. This feature (optional on the 3340, standard
on the 3344) disconnects the drive from the channel
and permits other channel operations to be performed
during the time required for the spindle to bring the
required record to the read/write head.
Additional details on RPS and its associated com-
mands are found in the following publications:
•Reference Manual for Integrated Storage
Control, Order No. GA26-1620.
•Reference Manual for 3830-2 Storage Control,
Order No. GA26-1617.
Fixed Heads
The 3340 fixed head feature permits use of the
3348-70F data module on any 3340 drive. This
70-megabyte data module contains fixed heads in
addition to the normal access heads. With these fixed
heads, 500 thousand bytes of storage are available that
have zero seek time. The feature does not increase
data module storage, because an equivalent amount of
storage under the moving heads becomes inaccessible.
The 3344-B2F dual-drive is also equipped with fixed
head storage. In this model, both 3344 drives have
1.004 million bytes of zero seek time storage. This
fixed head storage is associated only with the primary
addresses on each 3344 drive (see Figures 2and 3).
For further details on the fixed head feature and its
usefulness to your storage application, contact your
IBM sales representative or see the Fixed Head
Feature Users Guide, Order No. GA26-1632.
3340/3344 Storage Control and Features 3

CONFIGURATIONS
The various configurations of 3340/3344 disk storage
are divided into two groups: configurations using only
3340 units, and configurations using acombination of
3340 and 3344 units. These attachment methods,
listed by model, follow.
3340 STORAGE WITHOUT 3344
In some System/370 models, strings of 3330 and 3350
storage devices can be used in addition to the 3340s.
Model 115 (115DDA)
The Model 115 uses the Direct Drive Attachment
(DDA) for storage control. Four drives can be
attached: a3340-A2 dual drive with control, and a
3340-B2 (dual) orBl (single) drive.
Model 125 (125DDA)
The Model 125 uses the DDA for storage control and
can attach one string of up to eight 3340 drives.
Model 135 (IFA)
The Model 135 uses the Integrated File Attachment
(IFA) for storage control. Sixteen drives, two strings,
a3340 string and astring of either 3340 or
3333/3330 drives can be attached.
3340/3344 CONFIGURATIONS
When the 3344 is used, neither 3333/3330 nor 3350
drives can be attached to the same storage control.
A3344 requires four logical addresses for each drive.
Only the 135, 145, 155-11, 158, 165-11, and 168
support the 3344 dual drive.
Model 135 (IFA)
The Model 135 Integrated File Attachment has a
maximum of 34 logical addresses. This allows two
storage strings to be attached: a3340 string and a
3340/3344 string (see Figure 2).
Models 135, 145, 155-H, 158, 165-11, and 168
(3830-2) Models 145, 158, and 168 (ISC)
Sixty-four logical addresses can be used by a3830-2
or ISC path when a3340/3344 configuration is
attached. Two strings of 3340/3344s, a3340 string,
and ashort string of four 3340 drives can be
attached.
Figure 3shows the maximum 3340/3344 configura-
tion. Only strings and 2 can incorporate the 3344
units. Each drive has the hexadecimal addresses
assigned relative to the storage control as shown.
Models 135, 145, 155-H, 158, 165-11, and 168
(3830-2) Models 145, 158, and 168 (ISC)
Storage control for the models shown is either a
3830*2 or an Integrated Storage Control. The
3836-2 and each ISC path can attach up to 32 drives,
four strings of 3333/3330s, 3340s, or 3350s in any
combination.
4IBM 3340/44 Reference Manual

String
3340-A2 3344 3344 3344
3135
IFA
02* 03* 04* 05* 06* 07*
00 01 10
16
1C
11
17
1D
12
18
13
19
14
1A
20
15
1B
21
Drive
No.
1E 1F
!1
String 1
3340-A2
23
3340-B2
45
3340-B2
67
3340-B2
08 |09 0A |OB OC |OD OE |OF
Drive
No.
!1234567
*Primary Addresses
Figure 2. IFA 3340/3344 Maximum Configuration (Hexidecimal addressing)
String
3340-A2 3344 3344 3344
Storage
Control
02*
22
2A
03*
23
2B
04* 05* 06* 07*
00 01 24
2C 25 2D 26 2E
36
27
2F
37
Driw
No.
32 33 34 35
i1
String 1
3340-A2
23
3340-B2
45
3340-B2
67
3340-B2
08 |09 0A |OB OC |OD OE |OF
Drivi
No.
51
String 2
3340-A2
23
3344
45
3344
67
3344
10* 11* 14* 15* 16* 17*
12 13 20
28
21
29
1C
38
1D
39
1E
3A 1F 3B
Drivi
No.
30 31 3C 3D 3E 3F
i23
String 3
3340-A2
1
3340-B2
4567
1a'in
18 IC 1A
*Primary Addresses
Figure 3. ISC or 3830-2 3340/3344 Maximum Configuration (Hexidecimal addressing)
Configurations 5

IBM 3348 DATA MODULE
DATA MODULE TYPES
The 3340 models use the IBM 3348 Data Module as a
storage medium. Three types are available: the 3348
Model 35 with about 35 million bytes of storage, the
3348 Model 70 with about 70 million bytes of storage,
and the 3348 Model 70F with about 70 million bytes
including one-half million bytes under fixed heads.
The Models 35 and 70 can be freely exchanged on the
3340 drives, but the Model 70F can use its fixed heads
only on 3340 drives that have been converted for
Model 70F use.
The 3348-70F data module has the same characteris-
tics as the 3348-70 except that cylinders 1through 5
are accessed by the fixed heads. Data on tracks under
the fixed heads is available with only rotational delay.
The other tracks (cylinders and 6through 695) are
subject to normal head access delays.
The three data modules have the following characteris-
tics:
Byte Capacity
Per track
Per cylinder
Per module
3348-35
8,368
100,416
34,944,768
3348-70,-70F
8,368
100,416
69,889,536
DATA MODULE INITIALIZATION
All 3348 data modules are initialized when manufac-
tured. Home address and 8-byte descriptors (R0) are
written on each track. If askippable defect is found,
the written home address contains the skip displace-
ment bytes. During normal operations the storage
control uses the skip displacement bytes to bypass the
defective area. If amodule data area becomes defec-
tive during normal use, IBM utility programs are
available to flag defective tracks and assign alternates
if required (DASDR and ATLAS for OS and DASDI
for DOS).
DATA SURFACE FORMAT
The disk data surface is divided into concentric bands
of data called tracks (see Figure 4). Each data surface
uses two magnetic read/write heads, one for the inside
tracks and one for the outside tracks. The recording
surface of the disk is divided in half. All odd num-
bered tracks are on one side of the dividing line and all
even numbered tracks are on the other. The odd index
point starts the odd tracks and the even index starts
the even. When the heads are at agiven position,
they service four tracks: one odd, one even, one
inside, and one outside.
In the 3348-35 data module the tracks under the three
outside heads and those under the three inside heads
form acylinder. All odd numbered tracks are on one
side of the three disks and the even tracks on the other
side.
The 3348-70 data module contains four disks. The
track geometry is the same as that of the smaller data
module with acylinder available at each position. Odd
numbered cylinders are on the upper three surfaces
and the even cylinders are on the lower three. From a
single position two consecutive (even and odd)
cylinders can be accessed (see Figure 5).
The differences between the storage media used on the
3340 data storage units follow:
3348-35 3348-70
Data Surfaces per Module 22
Physical Heads per Surface 22
Logical Cylinders per Module 348
Alternate 1
CE 1
696
2
2
Logical Cylinders per Physical
Cylinder 12
Physical Tracks per Physical
Cylinder 612
Logical Tracks per Physical
Cylinder 12 24
Logical Tracks per Logical
Cylinder 12 12
Logical Tracks per Physical
Track 2 2
6IBM 3340/44 Reference Manual

70 Megabytes
Even «ndex Point
Figure 4. Data Surface Track Layout
Both Odd and Even
Cylinders. Odd tracks
follow odd index; even
tracks follow even index.
3348-35
Cylinders
001.003.
005. ...
(heads 6-11)
Odd index Point
Cylinders
000.002.
004....
(heads 0-5)
Odd Cylinders
001,003,
005 699,
(heads 6-11)
Even Cylinders
000, 002,
004 698.
(heads 0-5)
3348-70 *£. 5V
7«
11 10
8r
8*-
wmTQ
Data
Heads
Note: In the 3348-70F data module, cylinders 001-005 are
located on the bottom surface of the bottom disk.
Figure 5. Data Module Geometry
IBM 3348 Data Module 7

FORMATS
RECORD FORMAT
The basic unit of information recorded by the drive is
a byte consisting of eight bits. Agroup of bytes
separated by aspecial gap is called an area. Areas are
combined to make arecord, the logical unit of inform-
ation. Arecord consists of count, key, and data areas.
Count Area
The count area contains the location of adata record
on aspecific track and defines the size of the key and
data areas of the record. The count area is written
when the record is formatted and is not changed until
the record is reformatted.
Key Area
Use of the key area is at the discretion of the program-
mer. When used, the key area of the record contains
the primary identification of the data portion of the
record (such as social security number, man number,
part number).
Once the key area is formatted, the contents (but not
the length) may be altered. If the key area is altered,
the data area of the record must also be rewritten.
Data Area
The data area contains the information identified by
the count and key areas of the record. Data informa-
tion is organized and arranged by the programmer.
The length of the data area is defined by the count
area. Once the data area is formatted, the contents
(but not the length) may be altered. The contents of
the data area may be altered without affecting any
other area in the record.
TRACK FORMAT
All tracks are initially formatted beginning at an index
point (see Figure 6). Each track has the same basic
format: home address, track descriptor record, and one
or more data records. The records, and areas within
the records, are separated by gaps.
Home Address
Each track contains one home address, which defines
the physical location of the track (track address) and
the condition of the track. Home address is the first
recorded area following an index point.
Specific commands are used for writing and reading a
home address area: Write Home Address and Read
Home Address. Home address is normally rewritten to
flag the defective track. Writing home addresses is
usually done at the IBM plant.
Track Descriptor Record (RO)
This record is always the first record on the track
following the home address area. In IBM program-
ming systems, the RO count field of the defective track
provides the address of the alternate track. If it is an
alternate track, the RO count area proyides the address
of the defective track. An 8-byte data field is used to
store the number of bytes remaining on the track.
Specific commands, Write RO and Read RO, are used
for writing and reading the track descriptor record.
Data Records
One or more data records may follow the track
descriptor record (RO) on atrack. Record format is
determined at the time the count, key, and data areas
of the record are originally written by execution of a
Format Write command. The format of the record is
rewritten by another Format Write command.
Data records, as well as track descriptor records, can
be formatted with or without keys. Generally, file
organization determines whether keys are used.
RECORD OVERFLOW
The record overflow function provides ameans of
processing logical records that exceed the capacity of a
track. When using overflow records, the cylinder
boundary limits the size of the record.
8IBM 3340/44 Reference Manual

TRACK CAPACITY
The number of records that can be recorded on a
track depends on the record size. The following
equation can be used to determine the number of equal
length records per track. The home address and
standard RO space and skip defect are taken into
consideration.
Equal length records _8,535 (track capacity)
track C+KL +DL (bytes/record)
where:
C(overhead/record)= 167 if KL =
=242 if KL #
KL= Key length
DL= Data length
The number of records (n) of different key and data
lengths that can be recorded on atrack must satisfy
the following equation (the standard RO is already
accounted for):
Records n
Track =8,535 >£C+KL(») +DLG)
i= 1
When RO is not standard, the following formula should
be used:
Records =8,706 >[KL(o) +DL(o) +C-4] +
Track n
£[KL(i) +DL(i) +C]
i=1
where: C=167ifKL =
C-242 if KL #
The tables shown in Figures 7 through 10 give maxi-
mum sizes of n equal-length records on atrack where
nis all possible values. Track, cylinder, and data
module capacities are given in both the number of
bytes and the number of records.
There are tables for records without keys, and for
records with keys. In all tables, overhead for home
address and standard record zero (KL =0, DL =8) is
already accounted for.
where: C=167ifKL =
C=242 if KL /
Formats 9

-Track Format
Index
Record Zero RO
A
Home
Address
/
G2
/
/
RO Count
Area G2 ROKey
Area t
/
//
SD
1
PA FCC
1
HH
1
RK
LDL
...J,,.,
DCB G2 Key tDCB
G2 RO Data
Area
/
1/
/
/
G2 DATA DCB
tStandard RO does not contain an RO key area or associated gap.
System
IData
G3< (System/
'Storage
^Control)
(Disk to
JStorage
G3 ^Control
fData
INDEX: Indicates the beginning of each track. All tracks on
the disk surface are synchronized by Index.
G1 (Gap 1): Separates Index and Home Address.
HOME ADDRESS
SD (Skip Displacement): Storage control indicators for skip
displacement condition of track.
PA (Physical Address): Storage control check for
verification.
Note: The SD and PA bytes are internal conventions involv-
ing only the storage control and drive. The function is
transparent to the using system.
F(Flag): Defines track condition as follows:
Bit -Skip Displacement
Bits 1,2, 4, and 5-Unused.
Bits 6and 7-00 =Normal Track
01 =Alternate Track
10=)
11 =jDefective Track
The flag byte may be transferred to and from the using
system. It is the only flag byte transferrable.
CC (Cylinder Number): Specifies the cylinder number:
For 3348-35 to 347
For 3348-70 to 695
For 3348-70F to 695 (cylinders 1-5 fixed heads)
HH (Track Number): Specifies the read/write track number
with the selected cylinder:
For 3348-35 0-11
For 3348-70 0-11
For 3348-70F 0-1 1(cylinders 1-5 fixed heads)
DCB (Detection Code Bytes): Generated by the 3340-A2
and used for error detection.
Figure 6. Record and Track Format
10 IBM 3340/44 Reference Manual
G2 (Gap 2): Separates home address and R0 count area.
RECORD ZERO
R0 COUNT AREA
SD and PA: Same as Home Address.
F(Flag): Defines track condition identifier for overflow
records.
Bits 0—2 —Skip Displacement Indicators.
Bits 3and 5—Unused, bit 5is always zero.
Bit 4-When on, indicates that alogical record continues
on the next track.
Bits 6and 7-00 =Normal Track
01 =Alternate Track
10= )
11=/ Defective Track
CC (Cylinder Number): Specifies the cylinder number:
For 3348-35 to 347
For 3348-70 to 695
For 3348-70F to 695 (cylinders 1-5 fixed heads)
HH (Track Number): Specifies the read/write track number
within the selected cylinder.
For 3348-35 0-1
1
For 3348-70 0-1
1
For 3348-70F 0-1 1(cylinders 1—5 fixed heads)
R(Record Number): Normally has avalue of Hex 00.
KL (Key Length): Specifies the number of bytes in the R0
key area, from" 0—255 bytes. For standard R0, this normally
has avalue of Hex 00.
DL (Data Length): Specifies the number of bytes in the R0
data area, from 1to track capacity. For standard R0, this
normally has avalue of Hex 08.
DCB (Detection Code Bytes): Generated by the 3340-A2
and used for error detection.

Track Format
Data Record R1-Rn
A
System Data)
(System/
Storage
Control)
G3 R1-RnCnt
Area
KG2 R1-Rn Key
Area G2 R1-Rn Data Area
\\
Disk to
Storage ^G3
Controi
Data
SD
I
PA
I
FCC
I
H H
I
RK
LDL
I
DCB G2 Key
G4
Index
A
DCB G2 DATA DCB
G2 (Gap 2): Precedes all key areas.
RO KEY AREA
KEY AREA: Identifies information in the data area. For
standard RO, this area is not present on the track.
DCB (Detection Code Bytes): If key area is written, these
bytes are generated by the 3340-A2 and used for error
detection.
G2 (Gap 2): Precedes all data areas.
RO DATA AREA
DATA AREA: Contains the information identified by the
count and key areas.
DCB (Detection Code Bytes): Generated by the 3340-A2
and used for error detection and correction.
DATA RECORD COUNT AREA (R1-Rn)
G3 (Gap 3): Precedes all count areas, except RO,
DATA RECORD
DATA RECORD COUNT AREA
F(Flag): Same as Record Zero.
CC (Cylinder Number): Specifies the cylinder number:
For 3348-35 to 347
For 3348-70 to 695
For 3348-70F to 695 (cylinders 1-5 fixed heads)
HH (Track Number): Specifies the read/write track number
within the selected cylinder:
For 3348-35 0-11
For 3348-70 0-11
For 3348-70F 0-11 (cylinders 1-5 fixed heads)
R(Record Number): Specifies the sequential number of
the record on the track if specified by programmer.
KL (Key Length): Specifies the number of bytes in the
key area, from 0-255 bytes.
DL (Data Length): Specifies the number of bytes in the
data area, from 1to track capacity.
DCB (Detection Code Bytes): Generated by the 3340-A2
and used for error detection.
G2 (Gap 2): Precedes all key areas.
DATA RECORD KEY AREA (R1-Rn)
KEY AREA: Identifies information in the data area.
DCB (Detection Code Bytes): Generated by the 3340-A2
and used for error detection.
G2 (Gap 2): Precedes all data areas.
DATA RECORD DATA AREA (Rl-Rn)
DATA AREA: Contains the information identified by
the count and key areas.
DCB (Detection Code Bytes): Generated by the 3340-A2
and used for error detection and correction.
G4 (Gap 4): Padding from end of the last data area to
Index. If used for defect skipping, G4 is centered over the
defect. Formats 1
1

Record Length Track Capacity Cylinder Capacity
(DL) (Records) (Bytes) (Records) (Bytes)
(Bytes)
8,368 18,368 12 100,416
4,100 28,200 24 98,400
2,678 38,034 36 96,408
1,966 47,864 48 94,368
1,540 57,700 60 92,400
1.255 67,530 72 90,360
1,052 77,364 84 88,368
899 87,192 96 86,304
781 97,029 108 84,348
686 10 6,860 120 82,320
608 11 6,688 132 80,256
544 12 6,528 144 78,336
489 13 6,357 156 76,284
442 14 6,188 168 74,256
402 15 6,030 180 72,360
366 16 5,856 192 70,272
335 17 5,695 204 68,340
307 18 5,526 216 66,312
282 19 5,358 228 64,296
259 20 5,180 240 62,160
239 21 5,019 252 60,228
220 22 4,840 264 58,080
204 23 4,692 276 56,304
188 24 4,512 288 54,144
174 25 4,350 300 52,200
161 26 4,186 312 50,232
149 27 4,023 324 48,276
137 28 3,836 336 46,032
127 29 3,683 348 44,196
117 30 3,510 360 42,120
108 31 3,348 372 40,176
99 32 3,168 384 38,016
91 33 3,003 396 36,036
84 34 2,856 408 34,272
76 35 2,660 420 31,920
70 36 2,520 432 30,240
63 37 2,331 444 27,972
57 38 2,166 456 25,992
51 39 1,989 468 23,868
46 40 1,840 480 22,080
41 41 1,681 492 20,172
36 42 1,512 504 18,144
•31 43 1,333 516 15,996
26 44 1,144 528 13,728
22 45 990 540 11,880
18 46 828 552 9,936
14 47 658 564 7,896
10 48 480 576 5,760
749 343 .588 4,116
350 150 600 1,800
Figure 7. Record Capacities per Track and Cylinder -Without Keys
12 IBM 3340/44 Reference Manual

MODEL 35 MODEL 70/70F
Records Bytes Records Bytes
4,176 34,944,768 8,352 69,889,536
8,352 34,243,200 16,704 68,486,400
12,528 33,549,984 25,056 67,099,968
16,704 32,840,064 33,408 65,680,128
20,880 32,155,200 41,760 64,310,400
25,056 31,445,280 50,112 62,890,560
29,232 30,752,064 58,464 61,504,128
33,408 30,033,792 66,816 60,067,584
37,584 29,353,104 75,168 58,706,208
41,760 28,647,360 83,520 57,294,720
45,936 27,929,088 91,872 55,858,176
50,112 27,260,928 100,224 54,521,856
54,288 26,546,832 108,576 53,093,664
58,464 25,841 ,088 116,928 51,682,176
62,640 25,181,280 125,280 50,362,560
66,816 24,454,656 133,632 48,909,312
70,992 23,782,320 141,984 47,564,640
75,168 23,076,576 150,336 46,153,152
79,344 22,375,008 158,688 44,750,016
83,520 21,631,680 167,040 43,263,360
87,696 20,959,344 175,392 41,918,688
91,872 20,21 1,840 183,744 40,423,680
96,048 19,593,792 192,096 39,187,584
100,224 18,842,112 200,448 37,684,224
104,400 18,165,600 208,800 36,331,200
108,576 17,480,736 217,152 34,961,472
112,752 16,800,048 225,504 33,600,096
116,928 16,019,136 233,856 32,038,272
121,104 15,380,208 242,208 30,760,416
125,280 14,657,760 250,560 29,315,520
129,456 13,981,248 258,912 27,962,496
133.632 13,229,568 267,264 26,459,136
137,808 12,540,528 275,616 25,081,056
141,984 11,926,656 283,968 23,853,312
146,160 11,108,160 292,320 22,216,320
150,336 10,523,520 300,672 21,047,040
154,512 9,734,256 309,024 19,468,512
158,688 9,045,216 317,376 18,090,432
162,864 8,306,064 325,728 16,612,128
167,040 7,683,840 334,080 15,367,680
171,216 7,019,856 342,432 14,039,712
175,392 6,314,112 350,784 12,628,224
179,568 5,566,608 359,136 11,133,216
183,744 4,777,344 367,488 9,554,688
187,920 4,134,240 375,840 8,268,480
192,096 3,457,728 384,192 6,915,456
196,272 2,747,808 392,544 5,495,616
200,448 2,004,480 400,896 4,008,960
204,624 1,432,368 409,248 2,864,736
208,800 626,400 417,600 1,252,800
Figure 8. Record Capacities per Data Module -Without Keys
Formats 13

Record Length Track Capacity Cylinder Capacity
(KL+DL) (Records) (Bytes) (Records) (Bytes)
(Bytes)
8,293 18,293 12 99,516
4,025 28,050 24 96,600
2,603 37,809 36 93,708
1,891 47,564 48 90,768
1,465 57,325 60 87,900
1,180 67,080 72 84,960
977 76,839 84 82,068
824 86,592 96 79,104
706 96,354 108 76,248
611 10 6,110 120 73,320
533 11 5,863 132 70,356
469 12 5,628 144 67,536
414 13 5,382 156 64,584
367 14 5,138 168 61,656
327 15 4,905 180 58,860
291 16 4,656 192 55,872
260 17 4,420 204 53,040
232 18 4,176 216 50,112
207 19 3,933 228 47,196
184 20 3,680 240 44,160
164 21 3,444 252 41,328
145 22 3,190 264 38,280
129 23 2,967 276 35,604
113 24 2,712 288 32,544
99 25 2,475 300 29,700
86 26 2,236 312 26,832
74 27 1,998 324 23,976
62 28 1,736 336 20,832
52 29 1,508 348 18,096
42 30 1,260 360 15,120
33 31 1,023 372 12,276
24 32 768 384 9,216
16 33 528 396 6,336
934 306 408 3,672
Figure 9. Record Capacities per Track and Cylinder -With Keys
14 IBM 3340/44 Reference Manual

MODEL 35 MODEL 70/T70F
Records Bytes Records Bytes
4,176 34,631,568 8,352 69,263,136
8,352 33,616,800 16,704 67,233,600
12,528 32,610,384 25,056 65,220,768
16,704 31,587,264 33,408 63,174,528
20,880 30,589,200 41,760 61,178,400
25,056 29,566,080 50,112 59,132,160
29,232 28,559,664 58,464 57,119,328
33,408 27,528,192 66,816 55,056,384
37,584 26,534,304 75,168 53,068,608
41,760 25,515,360 83,520 51.030,720
45,936 24,483,888 91,872 48,967,776
50,112 23,502,528 100,224 47,005,056
54,288 22,475,232 108,576 44,950,464
58,464 21,456,288 116,928 42,912,576
62,640 20,483,280 125,280 40,966,560
66,816 19,443,456 133,632 38,886,912
70,992 18,457,920 141,984 36,915,840
75,168 17,438,976 150,336 34,877,952
79,344 16,424,208 158,688 32,848,416
83,520 15,367,680 167,040 30,735,360
87,696 14,382,144 175,392 28,764,288
91,872 13,321,440 183,744 26,642,880
96,048 12,390,192 192,096 24,780,384
100,224 11,325,312 200,448 22,650,624
104,400 10,335,600 208,800 20,671,200
108,576 9,337,536 217,152 18,675,072
112,752 8,343,648 225,504 16,687,296
116,928 7,249,536 233,856 14,499,072
121,104 6,297,408 242,208 12,594,816
125,280 5,261,760 250,560 10,523,520
129,456 4,272,048 258,912 8,544,096
133,632 3,207,168 267,264 6,414,336
137,808 2,204,928 275,616 4,409,856
141,984 1,277,856
i,
283,968 2,555,712
Figure 10. Record Capacities per Data Module -With Keys
Formats 15

INPUT/OUTPUT OPERATIONS
This section contains ageneral description of I/O
operations used with IBM disk storage devices.
Detailed information about the central processing unit
and channel program control of I/O operations is
found in IBM System/370 Principles of Operation,
Order No. GA22-7000.
DEVICE SELECTION AND ADDRESSING
Device Address
3340 DRIVES
Drive addresses are specified in the I/O instruction.
The 3340 address is specified in bits 4, 5, 6, and 7of
the address byte (byte 3); bit 3is also used with 32
drive addressing.
Any drive address from hex to Fcan be accepted.
Drives to 7are attached to the first controller string
and drives 8to Fon the second string. If alogical
connection cannot be made because the required drive
is offline, Unit Check (Intervention Required) is
returned. If multiple selection is detected because of a
hardware failure, Unit Check (Intervention Required)
is returned.
Note: The drive addresses must be wired on a
logic board in the drive units.
3344 DRIVES
For configurations using 3344 drives, the device
addressing is modified to handle the multiple logical
devices on each spindle. Bits 2through 7of byte 3
specify the logical device (a maximum of 64) and
bits and 1the storage control address. This
addressing allows 3344 drives on strings and 2only.
String 3can have only two 3340 units, one A2 and
one B(see Figure 3). When 3344 drives are attached
to astorage control, only 3340/3344 devices can be
controlled; 3330 or 3350 strings cannot be attached.
Seek Address
Aspecific track is selected by sending the seek address
and aSeek command to the required drive. These and
other commands are described in the ISC and 3830-2
reference manuals.
Bytes and 1are unused, bytes 2and 3are the logical
cylinder address, and bytes 4and 5are the logical
track address. All seek addresses consist of six bytes.
12 345
The CCHH part of count areas and home addresses
normally corresponds to bytes 2through 5of the seek
address. The physical address (PA) bytes in each
count area and home address indicate physical cylinder
and track addresses. The PA bytes are written by the
storage control and are used for seek verification.
When the seek argument is received by the storage
control, it is converted into physical cylinder and track
addresses and sent to the selected drive for Seek
operations. The acceptable seek addresses for the
3340/3344 devices are:
Storage
Model
Data Tracks Alternate Tracks
CC HH CC HH
3348-35 0-347 0-11 348 0-11
3348-70
3348-70F
0-695 0-11 696,697 0-11
3344-B2
3344-B2F 0-695
X4 0- 11 696,697
X4 0-11
ACCESS AND DATA TRANSFER SPEED
The total time required for access and data transfer
consists of access motion, head selection, rotational
delay, and data transfer.
Access Motion Time
Access motion time is the time required to move the
read/write heads to the correct cylinder. If the heads
are already at the correct cylinder, the access time is
zero. Access time is also zero for data stored under
fixed heads when fixed head models are used.
If the access mechanism must move to another cylin-
der, aminimum of 10 milliseconds is required. The
maximum access movement is 50 milliseconds, but the
average access time is 25 milliseconds.
Head Selection Time
The time required to select the read/write head is
negligible.
CCHH
16 IBM 3340/44 Reference Manual