IBM 3350-A2 User manual

Systems
GA26·1638-2 /
File No. 5370:07 ·
Reference Manual for
IBM 3350
Direct Access Storage

Preface
This publication is intended to familiarize data pro-
cessing personnel with the characteristics of IBM
3350
Direct Access Storage. The reader should have prior
knowledge of direct-access storage devices and
concepts.
The publication lists the functional characteristics and
describes the record format, capacity, and timing
characteristics. A list
of all commands executed by the
3350
is included in the Channel Commands section.
Suggested operator instructions are included in the
Operator Controls and Indicators section.
The following publications are recommended for
detailed information
con<:;erning the subjects covered
in this manual:
•
IBM System/370 Principles of Operation, Order
No.
GA22- 7000
• Reference Manual
for IBM 3830 Storage Control
Model
2, Order No. GA26-1617
Third Edition (April 1977)
• Reference Manual for IBM Integrated Storage
Control, Order No.
GA26-1620
• The functional characteristics manual applicable to
the parent system.
Order numbers for functional
characteristics manuals can be found in the
IBM
System/ 360 Bibliography, Order No. GC20-0360
and SystemI3 70 Bibliography, Order No.
GC20-0001.
• The Data Processing Glossary,
Order No. GC20-
1699, defines terms related to direct-access storage
devices.
• Additional information for use when planning a
3350 installation can be found in the 3350/ 3344
Installation and Conversion Guide, Order No.
GC20-1780.
If IBM 3350s are part of a system which includes the
IBM 3850 Mass Storage System, certain attachment
restrictions may apply. These restrictions are detailed
in the
IBM 3850 MSS Principles of Operation,
Order No. GA32-0029.
This publication replaces and makes the second edition of Reference Manual for
IBM 3350 Direct Access Storage, Order No. GA26-1638-1, obsolete. The
contents of Technical Newsletter GN26-0326 has been incorporated into this
edition.
Changes or additions are indicated by a vertical bar to the left of the
change.
Changes
or additions to the specifications contained in this publication are
periodically 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.
A
form 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, Technical
Publishing,
Department G26, 5600 Cottle Road, San Jose, California 95193.
©Copyright International Business Machines Corporation 1975, 1976, 1977.
ii IBM 3350 Reference Manual

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Highlights
.................................. l
General Description .......................... 1
IBM 3350 Attachment ........................ 3
Attachment to 3850 System .................. 3
Compatibility With Existing Storage
............. 3
IBM
3330 Model 1 Compatibility Mode ........ 3
IBM
3330 Model 11 Compatibility Mode ....... 3
IBM
3350 Native Mode ..................... 3
Models and Special
Features .................... 4
3350 Models ................................ 4
Special
Features ............................. 4
String Switch
............................. 4
Primary
Controller Adapter .................. 4
3350 Head/Disk Assembly .................... 5
Data Formats ................................ 6
Data Groups ................................ 6
Record Format .............................. 6
Count Area ............................... 6
Key Area ................................ 6
Data Area ................................ 6
Track Format ............................... 6
Home Address ............................ 6
Record Zero .............................. 6
Data Records ............................. 6
Write Padding
............................... 7
Track Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3330 Compatibility Modes................. 10
3350 Native Mode . . . . . . . . . . . . . . . . . . . . . . . 10
Input/Output Operations. . . . . . . . . . . . . . . . . . . . . 15
Drive
Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Drive Addresses . . . . . . . . . . . . . . . . . . . . . . . . . 15
Valid
3350 Addresses..................... 15
Seek Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . 17
Access and Data Transfer Time . . . . . . . . . . . . . . . 17
Seek Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Head Selection Time . . . . . . . . . . . . . . . . . . . . . 17
Latency................................ 17
Data Transfer Rate. . . . . . . . . . . . . . . . . . . . . . . 17
Data Integrity and Security. . . . . . . . . . . . . . . . . . . 18
Write
Protect . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Seek Verification . . . . . . . . . . . . . . . . . . . . . . . . 18
File Protection . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Contents
Error Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Error Correction Function . . . . . . . . . . . . . . . . . . . 19
Error Correction Table . . . . . . . . . . . . . . . . . . . . . . l9
Error Recovery Action . . . . . . . . . . . . . . . . . . . . . . 19
CCW Restart Construction . . . . . . . . . . . . . . . . 19
Error Correction Table. . . . . . . . . . . . . . . . . . . . 20
Recovery Action Table .................... 21
Channel Commands ......................... 25
Control Commands. . . . . . . . . . . . . . . . . . . . . . . . . 25
Search
Commands . . . . . . . . . . . . . . . . . . . . . . . . . 25
Read Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Sense Commands . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Format Write Commands. . . . . . . . . . . . . . . . . . . . 25
Update Write Commands . . . . . . . . . . . . . . . . . . . . 25
Sense
Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Sense Byte Summary. . . . . . . . . . . . . . . . . . . . . . . . 31
Sense Bytes 0- 7 Summary. . . . . . . . . . . . . . . . . . . . 32
Operator Controls And Indicators . . . . . . . . . . . . . . 43
Operator Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Ready Lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Attention Pushbutton. . . . . . . . . . . . . . . . . . . . . 43
Read,
R/W Switch . . . . . . . . . . . . . . . . . . . . . . . 43
Start/Stop Switch. . . . . . . . . . . . . . . . . . . . . . . . 43
Power Control Panel (A2/ A2F) . . . . . . . . . . . . . . 44
Power On Switch . . . . . . . . . . . . . . . . . . . . . . . . 44
Enable Power Off Switch . . . . . . . . . . . . . . . . . . 44
Power On Indicator . . . . . . . . . . . . . . . . . . . . . . 44
A and B Enable/Disable Switches . . . . . . . . . . . 44
Controller Assignment Panel (C2/C2F) . . . . . . . . 44
Primary
I Alternate Switch . . . . . . . . . . . . . . . . . 44
Primary/ Alternate Indicators (C2/C2F) ...... 44
Index
.................................... 45
Contents
iii

Illustrations
Figure l.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
IBM
3350 Disk Storage ............. 2
Basic
3350 Characteristics ........... 5
3350 Track Format ................. 8
Record Capacities, Without Keys . . . . 11
Record Capacities, With Keys . . . . . . 13
Drive Addressing. . . . . . . . . . . . . . . . .
15
Addresses for 3330-1 Compatibility
Mode . . . . . . . . . . . . . . . . . . . . . . . . . 16
Addresses for
3350 Native or
3330-11 Compatibility Modes ...... 16
Error Correction Table . . . . . . . . . . . . 20
Recovery Action Table . . . . . . . . . . . . 21
Control Commands. . . . . . . . . . . . . . . 26
Search Commands. . . . . . . . . . . . . . . . 27
Read Commands. . . . . . . . . . . . . . . . . 28
Sense
Commands ................ 29
Format Write Commands . . . . . . . . . . 30
Update Write Commands . . . . . . . . . . 30
Sense Bytes 0 through 7 Summary . . . 32
Sense Byte 0 Description . . . . . . . . . . 33
Sense Byte l Description . . . . . . . . . .
34
Sense Bytes 2 through 5 Descriptions. 35
Sense Bytes 6
and 7 Descriptions . . . . 36
Format Messages. . . . . . . . . . . . . . . . . 37
Format l Summary . . . . . . . . . . . . . . . 38
Format 4 Summary . . . . . . . . . . . . . . . 40
Format 5 Summary ....... , . . . . . . . 41
Format 6 Summary . . . . . . . . . . . . . . . 42
3350 Operator Panel. . . . . . . . . . . . . . 43
3350 Power Control Panel . . . . . . . . . 44
3350 Controller Assignment Panel. . . 44
iv IBM 3350 Reference Manual

The IBM 3350 Direct Access Storage provides fast-
access, large-capacity, high data-rate, low-cost, .
reliable online
data storage. The 3350 can be attached
to IBM System/370 Models 135, 138, 145. 148,
155-Il, 158, 158-3, 165-H, 168, and 168-3.
The 3350 offers significant cost/performance advan-
tages with increased recording density and a faster
data-transfer rate.
The 3350 selective format standard feature allows
each drive to operate in one of three modes: 3330-1
compatibility, 3330-1 l compatibility, or 3350 native.
To the system, a 3350 drive operating in a compatibili-
ty mode has the same characteristics as a 3350-1 or
3350-1 1. The track formats, tracks per cylinder, and
number of cylinders functionallv match those of the
I IBM 3330 Model 1 or the IBM '3330 Model 11.
Maximum capacity can be obtained by running the
string in the 3350 native mode.
The 3350 provides high-performance, large-capacity
storage for a wide range of applications such as:
• Data base/ data communications
• Inventory and manufacturing control
• Graphic processing
•
Time-sharing
• Message switching
• Systems residence
•
Other applications requiring direct or sequential
processing
HIGHLIGHTS
• Cost per byte: lower than any previous IBM disk
storage facility.
•
Storage capacity: 200 (3330 compatibility mode)
or 317 (native mode) million bytes per drive.
•
Data rate: 1198 thousand bytes per second.
• Seek time: an average of 25 milliseconds.
• Latency: 8.4 milliseconds (average).
• Command set: similar to the 3330 with a Read
Multiple Count, Key, and Data command.
• Rotational position sensing: standard feature.
Introduction
• Fixed head models: up to 2.2 million bytes per
model with zero seek time.
"' Security and privacy: write protection control
from operator panel, file protection, and seek
verification.
• Alternate conlroller feature: provides increased
data availability.
GENERAL DESCRIPTION
A 3350 Direct Access Storage subsystem consists of
from one to four dual-drive disk storage units. Three
types of 3350 are available; two with a controller and
drives, and one with only the drives. All 3350 units
arc available in models having fixed head storage. The
units use extensions of the technology developed for
the IBM 3340 disk storage with improvements that
increase storage capacity, data rate, and reliability.
The 3350 uses a sealed Head/Disk Assembly (HDA)
with 16 recording surfaces. The HDA is not remov-
able by the user. Fifteen surfaces are used for data
storage and one contains servo information for seek-
ing, track following, data clocking, generating the
index signal, and indicating the rotational position. In
models featuring fixed head storage, data is also stored
on the servo surface.
The first unit in each 3350 string must contain a
controller (Model A2 or A2F) and dual-drives. The
other units (up to three) consist of dual-drives (Model
B2 or B2F). Where increased data availability is
required, an alternate controller (Model C2 or C2F)
can be substituted for the last dual-drive unit. Models
A2F, B2F, and C2F provide up to 1.1 million bytes of
zero seek time storage per drive under fixed heads. If
an Alternate Controller model (C2 or C2F) is select-
ed, a maximum of two 82 or B2F models can be
installed between the A2/A2F and C2/C2F control-
lers.
Each of the eight drives (four dual-drive units) in a
storage subsystem can operate in one of three modes:
3350 native, 3330-1 compatibility, or 3330-11 com-
patibility. This selective format standard feature must
be specified for each individual drive at the time of
order and can be changed if required.
A functional
description of the 3350 models is shown
in Figure 1.
Introduction 1

3350-A2/A2F
3350-82/B2F
or
3350-C2/C2F
(shown)
IBM 3350-A2/A2F or C2/C2F (controller and two
drives)
CONTROLLER (only one controller in a string, A2/ A2F or
C2/C2F, can be online}
• Interprets and executes commands from the storage
control
• Regulates the storage control and disk drive
interfaces
• Checks data
integrity by error detection and error
correction functions
• Controls the writing and interpretation of the track
format fields
• Furnishes status and sense
information to the storage
control
• Performs diagnostic evaluation of the 3350 storage
string
• Serializes and deserializes data
• Provides and controls ac
power for the entire storage
string (A2/ A2F only)
DRIVES (A2/A2F, or C2/C2F has two independent drives)
• Responds to commands from the controller
• Positions access mechanism at a physical cylinder
• Selects the readI write head
•
locates a specified sector on a selected track
• Reads
or writes data
• Provides
safety and service information for evaluation
Figure I. IBM 3350 Disk Storage
2 IBM 3350 Reference Manual
IBM 3350-B2/B2F (two drives)
e Responds to commands from the controller
e Positions access mechanism at a physical cylinder
• Selects the readI
write head
•
locates a specified sector on a selected track
• Reads or writes data
• Provides
safety and service information for evaluation
IBM 3350-A2F, B2F, and C2F Models
• Native Mode -provides 1, 144 kilobytes of fixed head
storage
per drive with zero seek time.
•
Compatibility Mode -provides 742 kilobytes of fixed
head storage
per drive with zero seek time.

IBM 3350 ATTACHMENT
The 3350 can be attached to the following
System/370 systems:
Model Attachment Device
]35
3830-2
138
145
148
155-II
158*'
158-3
165-11
168,
168-3
Integrated Storage Control (ISC) or 3830-2
3830-2
Integrated Storage Control (ISC) or 3830-2
3830-2
Integrated Storage Control (ISC) or 3830-2
*Also 158 submode! 2 (Japan only)
Attachment of IBM 3350s to the systems shown may
involve additional requirements.
Attachment to IBM 3850 Mass Storage System
The 3350 DASD can be attached to the 3850 Mass
Storage System Staging Adapters as real spindles in
I
native mode; however, the 33 50s cannot be used for
3850 staging. A new feature, control store additional,
provides additional
microprogram storage to permit
3350 storage to be attached to IBM 3830 Model 3
Storage Control and to the 158/ 168 ISCs that have
staging
adapters on either one or both paths.
Expanded control store is a prerequisite for the new
feature on either the 3830-3 or ISC. Each 3350 string
can be made up of Models A2/ A2F, B2/B2F, and
C2/C2F in their normal configuration sequence. (See
Figure 1.)
COMPATIBILITY WITH EXISTING
STORAGE
Each 3350 drive is formatted at manufacture into one
of three operating modes: 3330-1 compatibility,
3330-11 compatibility, or 3350 native. Operational
modes can vary between drives on the same string or
unit.
IBM 3330 Model 1 Compatibility Mode
In the 3330-1 compatibility mode, a single 3350 drive
contains two logical 3330-1 volumes of data. Each
logical 3330-1 volume is equal to an actual 3330-1
volume in
capacity and format.
IBM 3330 Model 11 Compatibility Mode
In the 3330-11 compatibility mode, a 3350 drive holds
one logical 3330-11 volume of data. Eac,;h logical
3330-1 l volume is equal to an actual 3330-11 volume
in
capacity and format.
IBM 3350 Native Mode
In the 3350 native mode, the drive is used as a single
logical device with the full capacity of 317 ,498 kilo-
bytes of storage.
Introduction 3

Models and Special Features
The 3350 dual-drive storage units are available in six
models
and can incorporate the special features
described when required.
3350MODELS
Six 3350 models are available: the A2 (dual-drive
storage
and controller), the A2F (dual-drive storage
with fixed
heads and controller), the B2 (dual-drive
storage), the B2F (dual-drive storage with fixed
heads), the
C2 (dual-drive storage and alternate
controller), and the C2F (dual-drive storage with fixed
heads
and alternate controller).
The fixed heads on Models A2F, B2F, and C2F
provide up to 1.144 million bytes of zero seek time
storage
per drive. The fixed head storage capacity
takes the place
of an equal amount of storage under
the moving heads.
When a Model A2F, B2F, or C2F drive is used in the
3330-1 compatibility mode, the fixed head storage is
associated with the first of the two logical 3330-1
logical volumes
on the drive.
The C2 and C2F alternate controller models permit
the user to manually select
either the A2/ A2F or the
C2/C2F as the online controller. The other controller
drives
then function as a B2/B2F unit. If the online
controller requires service, manual switching
to the
other controller when preceded by a power off on the
A2/ A2F (by a switch on the C2/C2F) unit allows
subsystem availability
to be re-established.
When subsystem control has been switched from one
controller to the other, outstanding status and drive
reservations
(if any) are lost. Recovery/restart
procedures, required by the controller switchover,
must be
performed by the user.
Installation
of an alternate controller ( C2 or C2F) on
a 3350 subsystem requires that a primary controller
adapter feature be installed on the A2/ A2F control-
ler.
The basic 3350 characteristics are shown in Figure 2.
4 IBM
3350 Reference Manual
The fixed head storage capacity of Models A2F, B2F,
and C2F is:
3350 3330-1 or 3330-11
Native Mode Compatibility Mode
Logical Cylinders 1-2 1-3
Tracks 0-29 0-18
Tracks/Logical 30 19
Cylinder
Capacity /Drive
1,144,140 742,710
(bytes)
Capacity /Unit
2,288,288 1,485,420
(bytes)
SPECIAL FEATURES
Three special features are available for the IBM 3350
Direct Access Storage: string switch, remote switch,
and primary controller adapter.
String Switch
The string switch feature, available for all controller
models, allows a
3350 subsystem to be dynamically
shared by two storage controls. The 3350 can be
dedicated to a single storage control through use of the
Enable/ Disable switch. The string switch feature can
be installed on either or both controller units
(A2/ A2F and C2/C2F} in a string. If the string
switch feature
is installed on the A2/ A2F, it is recom-
mended that a string switch also be installed on the
C2/C2F to allow communication with more than one
storage control.
REMOTE SWITCH ATTACHMENT
The remote (Enable/Disable) switch allows the string
switch
to be controlled from the control panel of a
System/370 Model 158 or 168 Multiprocessor. The
string switch feature is a prerequisite for this feature.
Primary Controller Adapter
The primary controller adapter feature is required on
the A2/ A2F when a C2/C2F model is used. The
adapter permits the selection/ deselection of the
controller of the A2/ A2F unit as the online controller
through use
of a manual switch on the C2/C2F unit in
a
3350 subsystem.

The 3350 storage subsystem uses a sealed, head/ disk
assembly
(HDA) as the storage medium. The record-
ing heads and the carriage are
an integral part of the
HDA.
Characteristic 3350 in 3330-1
Compatibility Mode
(2 per drive)
Cylinders per drive
404 (plus 7
alternates)
Tracks per cylinder 19
Tracks per drive
7,676 (plus
133 alternates)
Track capacity
13,030
(bytes)
Cylinder capacity
247,570
(bytes)
Drive capacity
100 million
(approx bytes) (per logical volume)
Figure
2. Basic 3350 Characteristics
IBM 3350 Head/Disk Assembly
All 3350 drives are shipped formatted in the operating
mode specified by the customer.
If an HDA is to
operate in a different mode it can be reformatted with
an IBM supplied program.
3350 in 3330-11
3350in
Compatibility Mode Native Mode
808 (plus 7 555 (plus 5
alternates) alternates)
19
30
15,352 (plus 16,650 (plus
133 alternates) 150 alternates)
13,030 19,069
247,570
572,070
200 million 317.5 million
IBM 3350 Head/Disk Assembly 5

Data Formats
All 3350 drives are initialized at manufacture and
shipped with a home address and an eight-byte track
descriptor record (RO) written on all tracks. If the
data areas become defective during normal use, an
IBM utility program
is available to flag defective
tracks and assign alternates.
DATA GROUPS
The basic information unit stored by the drive is a byte
consisting of eight bits (binary digits). A group of
bytes separated by a gap is called an area. Areas and
gaps are combined to form a record, the basic informa-
tion unit.
RECORD FORMAT
A record consists of three specific areas: the count
area, the key area, and the data area (plus the neces-
sary gaps to
separate them). The process of writing an
entire record is called formatting.
Count Area
The count area contains the physical address of a data
record and defines the size of 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
The key area can be used to access data when organ-
ized in a keyed sequence. Primarily, it serves as an
identifier of the
data area that follows. Examples of a
key identifier are: a
part number, an employee num-
ber,
or a Social Security number.
After formatting, the key area length is fixed. The
contents of the area can be changed as required. If the
key area content is changed, the data area (which
follows) must also
be rewritten.
Data Area
The record's data area contains the information
addressed
and identified by the count and key areas.
This
data is organized and arranged by the program-
mer.
6 IBM
3350 Reference Manual
The data area length is defined by the count area.
Once formatted, the contents, but not the length, of
the data area can be changed without affecting the
count and key areas in the record.
TRACK FORMAT
Each track has the same format: a home address, a
track descriptor record, and one or more data records.
The records, and the areas in the records, are separated
by gaps. See Figure 3.
Home Address
Each track contains one home address (HA) defining
the physical location
of the track (track address) and
the
track condition. The home address is the first
recorded area following the index point.
Special commands are required to read
and write in the
home address area.
Track Descriptor Record
The track descriptor record is the first record following
the home add.ress area. In IBM programming systems,
the RO count area provides the address of an alternate
track if the track is defective. If the track is an alternate,
the address of the defective track is provided.
Special commands are required to read and write
data
in the RO area.
Data Records
One or more data records follow the track descriptor
record.
The data record format is determined when
the count, key, and data areas are originally written.
The number of data records per track is determined by
the number of bytes in each record and track capacity.
Data records, and track descriptor records, can be
formatted with or without keys depending on the
programmer's file organization.
OVERFLOW RECORDS
The record overflow function allows records exceeding
the track capacity to be continued on the next track
following
the HA and RO areas. These record seg-
ments can continue on successive tracks up to the
cylinder boundary.

WRITE PADDING
Write padding is a process of filling out the remaining
portion
of a track with a special pattern following
completion of format writing. Padding begins upon
completion of writing initiated by a format write
command if
another format write command is not
chained.
The
3350 (all modes) has a format write release
feature which
under some conditions allows the
storage control to disconnect after the last format
write
command on a track and to service other drives
while the original drive pads to
the end of the track.
In this case, index orientation may be lost upon
reconnection to the channel.
Data Formats 7

r
Index
Point
6
G1
,,..
/
Home
Address
INDEX POINT: Indicates the start of all tracks.
G1 (gap 1): Separates index and home address.
HOME ADDRESS
G2
Supplies basic track information, one per track following
index.
SD (Skip Displacement): Each two bytes give displace-
ment (in bytes) from index to track defect center and
displacement of the second defect center from the first
defect center, and the third defect center from the
second.
Note: The SD bytes are normally internal conventions
involving only the
storage control and drive. They are
transparent to the using system except: ( 1) they must
be
supplied by the system for a Write HA when the drive is in
3350 native mode; ( 2) the SD bytes, for use in item 1.
may be sensed by executing a Sense 1/0 chained from a
successful
Read HA.
PA (Physical Address): Storage control check for
address verification.
Note: The PA bytes are an internal convention involving
only the
storage control and the drive.
F (Flag): Defines track condition as follows:
Bit 0 Skip displacement
Bit 1 Unused
Bit 2 Indicates HA area moved for skip displace-
Bits 3 - 5
Bits 6, 7
00 =
01 =
10 =
11 =
ment
Unused
Track status
Normal primary
Normal alternate
Defective primary
Defective alternate
Note: This HA flag byte is the only flag that is transferred
between the using system and the drive.
Figure 3. 3350 Track Format
8 IBM 3350 Reference Manual
RO Count
Area
Record Zero RO
RO Data
Area
G3
CC (Cylinder Number): Specifies the cylinder number
under user control.
Native Mode
3330-1 Mode
3330-11 Mode
0-554
0-403
0-807
HH (Head or Track Number): Specifies the head (or
track) within the cylinder under user control.
Native Mode
3330-1 Mode
3330-11 Mode
0-29
0-18
0-18
,,
DCB (Detection Code Bytes): Generated by the 3350
controller and used for single error burst detection of ten
bits or less.
G2 (Gap 2): Separates home address and record zero
count areas.
RECORD ZERO
RO Count Area
SD· Similar to home address
PA: Same as home address
F (Flag): Defines track condition for overflow records:
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bits 6, 7
00 =
01 =
10 =
11 =
Defect in next count field
Defect in this key field
Defect in this data field
Unused
Logical record continues on next track
Unused
Track status
Normal primary
Normal alternate
Defective primary
Defective alternate

---- Track Format -------------------------------iaio1~
Data Record R1-Rn /
Index
-------------,
G3
R1-Rn Cnt
G2 G2 Reserve for Defects I
~rea .._ -:::'."", ______ -\
', -- ......... .._ ' -- ...... ..... \
' ......... "-.., .............. ........... - -........ ...... ..... ............ ',
'' -- ....... ...... --.. -'-.. \
1s
1
D1 s
1
DI ;~}I cc 1 "" Hrl DL}CB1:m :+.::1 CCB [~~J
RO Count Area (continued)
CC: Same as.home address
HH: Same as home address
R (Record
Number): Normally = 00 for record zero.
KL (Key Length):
Specifies length of record key area. If
no keys used, value is 00.
DL (Data Length):
Specifies length of data area.
DCB: Same as home address
G2 (Gap
2): Separates record zero count and key areas.
RO Key Area
KEY: Identifies information in data area. For a standard
RO, this area is not present.
DCB:
Same as home address. Not present with no RO
key area on track.
G2 (Gap 2): Separates record zero key
(if used) and data
areas.
RO Data Area
DATA: Contains information identified by count and key
(if present) areas. A
standard RO has eight bytes.
CCB (Correction
Code Bytes): Detects single error bursts
up to ten bits and corrects single error bursts up to four
bits.
G3 (Gap 3): Separates all records (except
RO) from each
other.
DATA RECORDS (Rl - Rn)
Rl - Rn Count Area
SD: Similar to home address
PA:
Same as home address
F: Same as record zero
CC:
Same as home address
HH: Same as home address
R (Record number): Identifies the number of the record
on
the track (if specified by the programmer).
KL (Key Length): Defines the length of the record key
area (in bytes).
If zero, the key area is omitted.
DL (Data Length): Defines the length of the record data
area (in bytes).
DCB:
Same as home address
G2 (Gap 2): Separates
the record areas.
Rl - Rn Key Area
KEY: Used to identify the information placed in the data
area. Use is
dependent on application and the program-
mer.
DCB:
Same as home address
G2: Separates record areas
Rl - Rn Data Area
DAT A: Contains the information identified by the count
and key (if present).
DCB:
Same as RO data area
G3: Separates the records on a track.
Data Formats 9

TRACK CAPACITY
The number of records that can be recorded per track
depends
on the record size and track capacity. The
following formulas can be used to determine the
number
of equal length records that can be placed on a
track.
The home address, RO space, and skip defect
allowance (overhead) has already
been accounted for.
3330 Compatibility Modes
Equal length records 13,165 (track capadty)
where:
track
C+KL+DL (bytes per record)
C = 135 if KL = 0
= 191 if KL # 0
KL = Key Length
DL = Data Length
Note: When
an end-of-file (EOF) mark is written,
the
DL in the count area must be zero. The storage
control, however, adds a one-byte data area when
writing the
EOF mark. Programmers working with
track balance routines must allow
for this byte by
subtracting one byte from the track balance remain-
ing. The standard 135-byte overhead allowance
should therefore
be increased to 136 for each EOF
written.
The
number of records (n) of different key and data
lengths that can be recorded on a track must satisify
one
of the following equations.
Where
RO is standard:
n
13,165 ~~ (KLi+DLi+C)
i= 1
Where RO is not standard: n
13,298 ~[KL(O)+DL(O)+C-10] +~ [KLi+DLi+C]
i=l
10 IBM3350 Reference Manual
3350 Native Mode
Equal length records
track
where:
19,254 (track capacity)
C+KL+DL (bytes per record)
C = 185 if
KL = 0
= 267 if KL# 0
KL = Key Length
DL = Data Length
The number of records (n) of different key and data
lengths that can be recorded on a track must satisify
one of the following equations.
Where
RO is standard:
n
19,254 ~~ (KLi+DLi+C)
i=l
Where RO is not standard: n
19,442 ~[KL(O)+DL(O)+C-3]+~ [KLi+DLi+C]
i= 1
Figures 4
and 5 give the maximum number of equal
length records
on a track. The track and cylinder
capacity in both
number of bytes and number of
records is shown. There are two tables, one without
keys, and
one with keys. For drives being used in
compatibility modes, use the capacity tables in the
Reference Manual
for IBM 3330 Disk Storage,
Order No. GA26-1615.

Record length
Track Capacity Cylinder Capacity
(Dl Bytes) (Records) (Bytes) (Records) (Bytes)
19,069
1 19,069 30
572,070
9,442 2
18,884 60
566,520 I
6,233 3 18,6991
90
560,970 I
4,628 4 18,5121
120
555,360
3,665 5
18,325
150
549,750
3,024 6 18,
144
1801
544,320
2,565 7
17,955 210
538,650
2,221 8 17,763 240
533,340
1,954 9
17,586 270
527,580
1,740 10 17,400
300
522,000
1,565 11 17,215 330
516,450
1,419 12 17,028 360
510,840
1,296 13 16,848 390 505,440
1, 190 14 16,660 420
499,800
1,098
15
16,470 450
494,100
1,018 16 16,288 480
488,640
947 17
16,099
510
482,970
884 18
15,912
540
477,360
828 19
15,732 570 471,960
777 20
15,540
600
466,200
731 21
15,351 6301 460,530
690 22 15,
180
660
455,400
652 23
14,996
690
449,880
617 24
14,808
720
444,240
585 25
14,625
750
438,750
555 26
14,430 780 432,900
528 27 14,256 810 427,680
502
28 14,056
840
421,680
478
29
13,862
870 415,860
456
30
13,680
900
410,400
436 31 13,516
930
405,480
416 32 13,312
960
399,360
398 33 13,
134
990
394,020
381 34 12,954 1,020 388,620
365
35 12,775 1,050 383,250
349 36
12,564
1,080 376,920
335 37
12,395 1,110 371,850
321 38 12,198 1, 140 365,940
308 39
12,012
1, 170 360,360
296 40 11,840 1,200 355,200
284 41 11,644 1,230 349,320
273 42 11,466 1,260 343,980
262 43 11,266 1,290
337,980
252
44 11,088 1,320
332,640
242 45 10,890 1,350 326,700
233 46
10,718
1,380 321,540
224 47 10,528 1,410 315,840
216 48
10,368
1,440 311,040
207 49 10,143 1,470 304,290
200 50 10,000 1,500 300,000
192 51 9,792 1,530 293,760
Figure 4. Record Capacities, Without Keys (Part I of 2)
Data Formats 11

Record Length Track Capacity Cylinder Capacity
(DL Bytes) (Records) (Bytes) (Records) (Bytes)
185 52 9,620 1,560 288,600
178
53
9,434 1,590 283,020
171
54 9,234 1,620 277,020
165 55
9,075
1,650 272,250
158 56
8,848 1,680 265,440
152 57
8,664 1,710
259,920
146
58
8,468 1,740 254,040
141
59
8,319 1,770 249,570
135 60
8,100
1,800 243,000
130
61 7,930 1,830
237,900
125
62 7,750 1,860 232,500
120 63 7,560 1,890 226,800
115
64 7,360
1,920
220,800
111 65 7,215 1,950 216,450
106 66
6,996 1,980 209,880
102 67 6,834
2,010 205,020
98 68
6,664 2,040
199,920
94 69 6,486 2,070
194,580
90
70 6,300 2,100 189,000
86
71 6,106 2, 130
183,180
82 72
5,904 2, 160 177,120
78 73 5,694 2, 190
170,820
75 74
5,550 2,220 166,500
71 75 5,325 2,250 159,750
68
76 5,168
2,280 155,040
65
77 5,005 2,310 155,150
61
78 4,758 2,340
142,740
58
79 4,582 2,370 137,460
55
80 4,400 2,400
132,000
52 81
4,212 2,430 126,360
49
82 4,018
2,460 120;540
46 83
3,818 2,490
114,540
44
84 3,696 2,520
110,880
41 85 3,485
2,550 104,550
38 86
3,268 2,580 98,040
36
87 3, 132 2,610 93,960
33
88 2,904 2,640
87,120
31
89
2,759 2,670
82,770
28
90 2,520 2,700
75,600
26
91 2,366 2,730 70,980
24
92
2,208 2,760
66,240
22
93
2,046 2,790 61,380
19 94
1,786 2,820
53,580
17 95
1,615 2,850
48,450
15 96
1,440
2,880
43,200
13
97 1,261 2,910
37,830
11 98
1,078 2,940
32,340
9 99 851
2,970 26,730
7 100 700
3,000
21,000
5 101 505
3,030 15, 150
3
102 306
3,060
9, 180
1 103 103
3,090 3,090
Figure 4. Record Capacities, Without Keys (Part 2 of 2)
12 IBM 3350 Reference Manual

Record length
Track Capacity Cylinder Capacity
(Dl Bytes) (Records) (Bytes) (Records) (Bytes)
18,987 1 18,987 30
569,610
9,360 2
18,720
60
561,600
6, 151
3
18,453 90 553,590
4,546
4 18,
184 120 545,520
3,583 5 17,915
150 537,450
2,942
6 17,652
180 529,560
2,483 7 17,381
210
521,430
2,139 8 17,112
240 513,360
1,872 9 16,848 270
505,440
1,658 10 16,580 300 497,400
1,483
11
16,313
330
489,390
1,337 12 16,044 360 481,320
1,214 13 15,782 390 473,460
1,108 14
15,512 420 465,360
1,016 15 15,240 450 457,200
936 16
14,978
480
449,280
865 17 14,705 510
441, 150
802 18
14,436
540
433,080
746 19 14, 174 570 425,220
695 20 13,900 600
417,000
649 21 13,629 630
408,870
608 22 13,376 660
401,280
570 23 13, 110 690
393,300
535
24 12,840 720
385,200
503 25
12,575 750 377,250
473 26 12,298
780 368,940
446
27
12,042 810 361,260
420 28 11,760 840 352,800
396 29 11,484 870 344,520
374
30
11,220 900
336,600
354 31 10,974
930 329,220
334 32 10,638 960 320,640
316 33 10,428 990 312,840
299 34 10,
166
1,020 304,980
283 35
9,905 1,050
297, 150
267
36
9,612 1,080 288,360
253
37 9,361 1,
110 280,830
239 38 9,082 1, 140 272,460
226 39
8,914
1, 170 264,420
214 40 8,560 1,200 256,800
202 41 8,282 1,230
248,460
191 42 8,022 1,260
240,660
180 43 7,740 1,290
232,200
170
44
7,480
1,320 224,400
160 45 7,200 1,350
216,000
151 46 6,946 1,380
208,380
142 47 6,674 1,410
200,220
134
48 6,432 1,440
192,960
125 49 6, 125
1,470 183,750
118 50 5,900
1,500 177,000
110 51 5,610 1,530
168,300
Figure 5. Record Capacities, With Keys (Part I of 2)
Data Formats 13

Record Length Track Capacity Cylinder Capacity
(DL Bytes) (Records) (Bytes) (Records) (Bytes)
103
52
5,356 1,560 160,680
96 53
5,088 1,590
152,640
89
54 4,806 1,620 144, 180
83 55
4,565 1,650
136,950
76 56
4,256
1,680 127,680
70 57 3,990
1,710
119,700
64
58
3,712 1,740 111,360
59 59
3,481 1,770 104,340
53 60
3, 180 1,800 95,400
48
61
2,928 1,830 87,840
43 62
2,666 1,860 79,980
38
63
2,394 1,890 71,820
33
64
2, 112 1,920 63,360
29 65 1,885 1,950 56,550
24
66
1,584 1,980 47,520
20
67
1,340 2,010 40,200
16
68
1,088 2,040 32,640
12
69
828 2,070
24,840
8 70
560
2,100 16,800
4
71 284
2,130 8,520
Figure 5. Record capacities, With Keys (part 2 of 2)
14 IBM 3350 Reference Manual

This section describes the Input/Output operations
used with the 3350. Additional information about the
central processing unit
(CPU) and channel program
control of
I/0 operations is found in The IBM
System/ 370 Principles of Operation.
DR.IVE MODES
Each 3350 drive can be operated in one of three
modes: 3330-1 compatibility, 3330-11 compatibility,
or 3350 native. Units are shipped with drives format-
ted in the mode as specified by the customer. Changes
in mode require
CE and customer action.
Drive Addresses
The I/O drive address is an 8-bit byte plus a parity bit
(Figure 6). The parity bit
is discarded after a check is
made for odd parity and the remaining eight bits are
used to designate the required drive.
Bits 0 and 1 are the storage control address bits.
If a
non-existent storage control is addressed, condition
code 3
is indicated.
On all real 3330, 3340, or 3350 drives operating in
either native or 3330-11 mode, there
is only one
logical volume
on a drive. When a 3350 is operating in
the 3330-1 mode, there are two logical volumes
on a
drive.
The bit 2 function depends
on the string configuration.
If the storage control has no 3350 operating in the
3330-1 compatibility mode attached, bit 2 (together
with bits 0 and 1) functions as a storage control
address bit.
If any attached 3350 drives are operating in the
3330-1 compatibility mode, bit 2
is used to select the
correct logical device
on the drive. When bit 2 is off
(0), the primary logical device
on the drive is ad-
dressed. When bit 2
is on (1), the secondary logical
device
is addressed.
Bits 3 and 4 are the string address. This allows a
maximum of four storage strings to be attached to one
storage control. Each string (of up to eight physical
drives) may contain only 3350s, or only 3330s, or only
3340s (not 3344s); the
3350 strings can be in any
combination of compatibility and native mode 3350s.
If bits 3 and 4 address a string that is non-existent,
powered off, or disabled by the string switch, condi-
tion code 3
is indicated.
Page of GA.26-1638-1
Revised Jan. 31, 1978
By TNL: GN26-0342
Input/ Output Operations
Bits 5, 6, and 7 select one of the eight drives on the
string. Unit check
is returned if the drive is powered
down
or non-existent. Addresses of the storage
controls and string controllers are established
by the
user
and plugged at installation by the CE.
A maximum of
32 physical drives can be addressed
through a single storage control. When 3350s are
operating in the 3330-1 compatibility mode, 64 logical
drive addresses are available. Smaller configurations
of 8, 16, or 32 drives can be addressed
but require
different plugging arrangements by the CE. The
smaller addressing configurations require fewer unit
control words to be available in the channel.
Valid 3350 Addresses
When any 3350 is operating in 3330-1 compatibility
mode there are 36 valid secondary address ranges as
shown in Figure
7. The 3350 operates as two 3330-ls
and requires two logical addresses per spindle. When a
3350 is not operating in the 3330-1 compatibility
mode and 3330s
and/ or 3340s are attached to the
storage control, only primary addresses can be used.
When the 3350s are operating in either 3330-11
compatibility
or 3350 native mode, 72 valid address
ranges are available for each storage control. These
address ranges are shown in Figure 8.
Additional addressing information is found in the
applicable storage control reference manual and in the
3350/3344 Installation and Conversion Guide.
0 I 1 2" 3*
I
4* 5 I 6 I 7
Logical
Drive
Storage
Selection
String
Control
(3330-1
Address
Physical Drive
Address
Compati-
(max. Li,)
Address (max. 8)
bility
Mode
only) __j_
" When less than 64 addresses are configured, bits 2
through 4 can become part of the storage control
address.
Figure
6. Drive Addressing
Input/Output Operations 15

I Primary j Secondary Addresses
~~.dresses I Addresses ReQuired
L---_0 __ 0-_0_7 __ ,__ __ 2_0-_2_7 __ .__ __ 1_6 _ ____,
I 00-01_ 10--11 20-21, 30-37 32
I 00-0F I 20-2F 32
00-1 F 20-3F 64
08-0F I 28-2F 16
----it-------+------~
08-0F, 18-1 F I 28-2F, 38-3F 32
I I
I 10-17 I 30-37 16
~------+--------1---------1
i 10-ff i 30-3F 32
i-------------+-------+-------;
! 18-1F 38-3F 16
----+-------+-------I
40-41 I 60-s1 16
I
L 40-47, 50-57 60-67, 70-77 32
I 40-4F I 60-6F 32
I 50-5F 70-7F 32
r---------·------+-------+-------1
I . 58-5F __ +i ___ 7_8_-7_F __ -+- ___ 16_~-1
r----8_0-_8_7 ___ ,__ __ A_O-_A_7 ______ 1_6 _ ____,
-80-87, 90-97 AO-A7, B0-87 32
r 80-8F AO-AF 32
,____ __ _
! 80-9F 1 AO-BF 64
l _____ 8_8_-8 __ F __ ~!'-- __ A_8_-_A_F __ +- __ 1_6 __ ~
Lss-sF, 98-9F AB-AF, BS-BF 32
~ ___ 90-J)_J __ ~, ___ B_0_-_8_7 __ --+- __ 1_6 __ __,
L_ _jl0-9F~, ___ B_O_-_B_F __ +- __ 3_2 __ ~
L 98-9F 88-BF 16
I CO-C7 EO-E7 16
r-----------+--------+--------1
I CO-C7, 00-07 EO-E7, FO-F7 32
I CO-CF I EO-EF 32
r------------~---~-------<
L _____ c_o_-o_r_: __ 1- __ E_O_-_F_F __ --1- __ 6_4 __ ~
!
i C8-CF E8-EF 16
r CS-CF, 08-DF E8-EF, F8-FF 32
~-Dc;--D--7----+---F-O--'---F7----+----1-6--~
1- DO-OF I FO-FF 32
! !
L ___ __Q_§::__9_i ___ ~l ___ F_8_-F_F __ ~ ___ 16 __ ~
Figure 7. Addresses for 3330-1 Compatibility Mode
16 IBM 3350 Reference Manual
Address Ranges Addresses Address Ranges
from 00 to 7F Required from
80 to FF
00-07
8
80-87
00-07, 10-17 16 80-87, 90-97
00-0F 16
80-8F
00-1 F 32 80-9F
08-0F 8 88-8F
08-0F, 18-1 F 16 88-SF,
98-9F
10-17
8
90-97
10-1 F 16
90-9F
18-1 F 8
98-9F
-20-27 8 AO-A7
20-27,
30-37 16
AO-A7, B0-87
20-2F
16
AO-AF
20-3F
32
AO-BF
28-2F 8
A8-AF
28-2F, 38-3F 16
A8-AF, 88-BF
30-37
8
80-87
30-3F 16 BO-BF
38-3F 8
88-BF
40-47
8 CO-C7
40-47, 50-57 16 CO-C7,
D0-07
40-4F
16 CO-CF
40-5F
32
CO-DF
48-4F
8 C8-CF
48-4F,
58-5F
16 C8-CF, D8-DF
50-57
8
D0-07
50-5F 16 DO-DF
58-5F
8
08-DF
60-67
8
EO-E7
60-67, 70- 77 16 EO-E7, FO-F7
60-6F 16
EO-EF
60-7F 32
EO-FF
68-6F
8 E8-EF
68-6F,
78-7F 16 E8-EF, F8-FF
70-77
8
FO-F7
70-7F
16 FD-FF
78-7F
8 F8-FF
Figure 8. Address Ranges for 3350 Native or 3330-11 Compati-
bility Mode