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GC21-5040-3
\----. File No. 53-05
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P a g eo f G C 2 1 - 5 O 4 0 - 3
lssued 0 June1978
3
By TN L: GN21"5604
Fourth Edition (March19761
T h i s i s a m a j o r r e v i s i o no f , a n d o b s o r e t e s G C 2 r - b 0 4 0 - 2 . T h i s r n a n u a rh a s b e e n
, changeo
t o a n c l u d e h e M o d e i B a n d t h e M o d e l 1 2 . C h a n g e s r e i n d i c a t e db y a
t a ver.ticaline at the
l e f t o f t i r e c h a n g e ;n e w o r e x t e n s i v e r yr e v i s e di i l u s t r a t i o n sa r e d e n o t e d b y
a builet oat
the left t)f the figure caption.
c h a n g e sa r e p e r i o d i c a l l y m a d e t o t h e i n { o r m a t i o n h e r e i n ;b e f o r e u s i n g t h i s p u b r i c a t i o n
I n c o n n e c t i o n w i t h t h c o p e r a t i o n . r r B M s y s t e m s ,r e t e f t o t h e
r a t e s tt g M s y s t e m / 3
Bibliography, Gc20-8080 f or the editi'ns that are appricabreand current.
U s e t h i s p u b l l c a t i o n c n l y f o r t h e p u l p o s e ss t a l e d i n t h e p r e f a c e .
P u b l i c a t i o n sa r e n o t s t o c k e d a t t h e a d d r e s sb e l o w . R e q u e s t sf o r c o p i e s o f I B M p u b l i c a t i o n s
a n d f o r t L e c h n i c an f o r m a t i o n a b o u t t h e s y s t e ms h o u l d b e m a d e t c )y o u r l 6 M r e p r e s e n t a t i v e
il
o r t o t h e I B M b r a n c h o f f i c e s e r v i n gy o u r i u r : a l i t v ,
T h i s p r L r l i c a t i o n o u l d c o n t a i n t e c h n i c a l i n a c c , . L : " a coe s y p o g r a p h i c a le r r o r s . u s e t h e
c ir t
R e a d e r ' sc o m m e n t F o r m a t t h e b a c k o i t h i s p u b ! i i : a t i o n t o m a k e c o . r n m e n t s b o u t t h i s
a
p u b i i c a t i o n . l f t h e f o r m h a s b e e r rr e r n o v e d ,a d d r e s s
Vr:urcomments to iBM Corporation,
P u b l i c a t i o n s ,D e p a r t m e n t 2 4 5 , R o c h e s t e r 'f,i 4 i r n e s o r , 5 F 9 0 1 . c o m m e n t s b e c o n r et h e
a
property'oflBM.
O C o p y r i g h t l n t e r n a t i o n a l B u s i n e s s a c h i n e sC o r p o r a t i o n 1 g 7 1 . 1 g - 1 4 .1 g 7 6
M
Page GC21-5040-3
of
lssued June1978
30
By TNL: GN21-5604
Preface
This manualintroduces you to the 3410/341 Magnetic 1
T a p eS u b s y s t e m r t h e I B M S y s t e m / 3 . h i sm a n u a w i l l
fo T l
help installation managers decideif they want to usemag-
netictapeand aid in evaluating effect that it will have
the
on their currentoperations.Informationcontained the in
m a n u aw i l l a i d i n p l a n n i n go r t h e u s eo f m a g n e t i t a p e .
l f c
The manualcontains:
A description magnetic
of tape
A description the organizations tapefiles
of of
A description tape labels
of
A description control statement
of requirements
program
A description the Tape Initialization
of
A description the functionssupported RPG ll,
of by
C O B O L ,F O R T R A Nl V , B a s i c s s e m b l e D i s kS o r t ,
A r,
Magnetic Character Reader Utility. and TapeSort
programproducts
shouldbe familiarwith the operation
The reader and
programmingconcepts the System/3.
of
A glossary provided the backof this manualto define
is at
importantterms.
Page GC21-5040-3
of
lssued June1978
30
By TNL: GN21-5604
Related Publications
OrderNumberof Publication
for
System/3 System/3 System/3 System/3 System/3
M o d e l1 0 Model8 Model 10 M o d e l1 2 M o d e l1 5
Card System Disk System
O p e r a t o r 'G u i d e
s GC21.75'13 GC21-7634 i:ii::!:!it!iiiiiiitiitiii!:ii:i::i::i::i::ii:ii.ii:ii,i:,ii,:,i,:ii:i,:,i:i:::i::i::i:::i::iiii:it::i::i::i::i::i:iii;i:
R P Gl l R e f e r e n c e
Manual sc21-7500 sc21-7504
SystemControl GC21-5077r
Programming GC21-7512 GC21-5130 GC21-51622
R e f e r e n cM a n u a l
e
H a l tG u i d e
(System Messages) GC21-7540 GC21-5145 GC21.5076
SystemControl
P r o g r a m m i n ga c r o s
M GC21-7562 GC21-7608
Reference Manual
.iiiiiiiijiiiiiiiiiiitit]:.iix.itiiitiiiiiiiiiiii1111111.rrri.
User's uide
G '... r.........,............,........11iii:ii1it1
GC21-5142
Disk Concepts and GC21.7571
P l a n n i nG u i d e
g
S u b s eA m e r i c a n
t
N a t i o n aS t a n d a r d
l GC28-6452
C O B O LR e f e r e n c e
Manual
FORTRANV I sc28-6874
R e f e r e n cM a n u a l
e
Basic ssembler
A
R e f e r e n cM a n u a l
e sc21-7509
D i s kS o r t
R e f e r e n cM a n u a l
e ::::::::::::.:.:.:.:.:.::::::::::::
iiiiiiili:fi:i:r::
:::::::::::::::::.:!i.::: :::.:
:.:
sc21-7522
TapeSort
R e f e r e n cM a n u a l
e sc21-7572
Components
R e f e r e n cM a n u a l
e GA21.9236
l Models
1 5 A .B , c
2M o d e l
15D
Contents
CHAPTER 1. INTRODUCTION 1 C H A P T E R . 3 4 1 0 1 3 4 1 1M A G N E T I C T A P E
5
z SUBSYSTEM 25
Advantages f a TaPeSYstem
o
S o e c i a lF e a t u r e s . 25
zo
CHAPTER 2. MAGNETIC TAPE CONCEPTS 3 S i n g l eD e n s i t y T a P e U n i t F e a t u r e .
zb
R e c o r d i n g D a t a o n M a g n e t i cT a P e J Dual Densitv TaPe Unit Feature
? Seven-Track aPe Unit Feature
T 26
File Protection
Dual Density Control Feature 26
I n t e r s y s t e mT a p e E x c h a n g e
2 S e v e n - T r a c kC o n t r o l F e a t u r e 26
Tape File Formats
Tape Labels
J APPENDIX A. TAPE LABEL FORMATS 27
External Labels
lnternal Labels
? Volume Label Format
o HeaderLabel 1 and Trailer Label 1 Formal 2A
Taoe Record Attributes 29
Fixed Length Records o HeaderLabel 2 and Trailer Label 2 Format
Variable Length Records 6
GLOSSARY 31
Tape Blocking Factors 6
T a p e C t r a r a c t e rC o d e s 7
32
ASCIIFiles 1 INDEX
E B C D I CF i l e s 1
CHAPTER 3. MAGNETIC TAPE SYSTEMSUPPORT 8
Control Statement Requirements 8
M o c i e l1 0 C a r d S y s t e m 6
Model 8. Model 10 Disk System,Model 12, and
Model 15
Keyword Parametersor the FILE Statement
f 9
Tape Data Management 13
End of Volume Processing 13
D u a l P r o g r a m m i n g M o d e l s8 , 1 0 , a n d 1 2 ) o r
(
MultiprogrammingModel15) ( 13
M a g n e t i cT a p e U t i l i t y P r o g r a m s 14
Tape Initialization rogram P 14
Control Statements 14
C H A P T E R 4 . M A G N E T T CT A P E P R O G R A M P R O D U C T
SUPPORT 17
CardRPG ll for Model I U
D i s k R F G l l f o r M o d e l s8 , 1 0 , 1 2 a n d 1 5 18
S u b s e tA N S C O B O L 18
FORTFAN IV 19
1 0
M a g n e t i c C h a r a c t e rR e a d e r U t i l i t y P r o g r a m '19
Tape Sort Program
S y s l e mR e q u i r e m e n t s 19
Tape Sort Files 19
Sorl Functions 20
Record Selection 20
FieldSelection 20
A c l c l i t i o n a lF e a t u r e s. 20
B a s i cA s s e m b l e r 22
Disk Sort Program 22
S p e c i a lC o n s i d e r a t i o n s o r V a r i a b l e L e n g t h R e c o r d s
f 22
ZJ
M a g n e t i cT a p e S u P P o r t S u m m a r Y
Chapter Introduction
1.
The IBM 3410/3411Magnetic TapeSubsystem (Models1,
2. and 3) readsand writeshalf-inch, or 9-trackmagnetic
7-
tape. The subsystem provides economical
an approachfor
increasing storage
the capacity the IBM System/3. (Seven-
of
track magnetic tape is not available the Model 10 Card
for
System. )
3411 341
0 3410 0
341
Magnetic Magnetic Magnetic Magnetic
Tape Unit Tape Tape Tape
and Control Unit Unit Unit
System/3 supports maximumof four tape units. The
a
3 4 1 1 i s r e q u i r e d .U p t o t h r e e3 4 1 0 sc a nb e a t t a c h e d i a
v
the 34'11provided the 3410sarethe samemodelasthe
ul1.
Introduction 1
Page GC21-5040-3
of
lssued June1978
30
By TNL: cN2l-5604
ADVANTAGES OF A TAPE SYSTEM
Thereareother advantages usingmagnetic
in tape:
Largeamounts datacan be storedeconomically.
of
With appropriatespacingbetween groups records,
of
approximately 112 boxesof System/3 96-columncards
can be storedon a 2400-foot reel of tape.
Historyfilescan be retainedindefinitely.
Compared with cardsor diskettes,records tape may be any
on
size(within limits)depending the storage
on capacity the
of A duplicate disk pack records be kept.
of can
processing and the program
unit products the system(see
for
Magnetic TapeSupport Summary for allowable record Informationcan be transferred
easily other data
to
lengths).This allowswriting pertinentinformationin a processing
locations.
continuous data record. Repeating identification
the in
multiplerecords eliminated.
is System/3 magnetic tape is compatible
with magnetic
tapefor other systems.
Magnetic tape records, disk records, permanenr.
like are
However, duringa tapewrite operation, previously
the
recordedinformationis erased.This means that tapemay
be usedagainand againwith a significant
costsaving over
the useof cards. Diskettes alsoreusable.
are
P a g eo f G C 2 1 - 5 0 4 0 - 3
lssued 0 June 1978
3
Bv TNL: cN21-5604
Chapter2. MagneticTape Concepts
R E C O R D I N GD A T A O N M A G N E T I C T A P E T h e f o r m a t s o f t h e l a b e l e df i l e s a r e s h o w n i n F i g u r e s1 a n d
2 ; t h e f o r m a t s o f t h e u n l a b e l e df i l e s a r e s h o w n i n F i q u r e s
Data is recorded by moving tape acrossa read/write head. 3 and 4.
It iswritten while the tape is movingforward but may be
r e a de i t h e r f o r w a r d o r b a c k w a r d . D a t a i s w r i t t e n a s a s e r i e s T h e l a b e l so f e a c h r e e l o f a m u l t i v o l u m e f i l e m u s t o e
o f m a g r r e t i z e d i t s i n p a r a l l e lt r a c k s a l o n g t h e l e n g t h o f t h e
b c o n s i s t e n t .T h a t i s , a l l v o l u m e so f a l a b e l e dm u l t i v o l u m e
t ap e . f i l e m u s t b e l a b e l e d , n d a l i v o l u m e so f a n u n l a b e l e d
a
m u l t i v o l u m ef i l e m u s t b e u n l a b e l e d .
T h e r e c o r d i n gd e n s i t y i s t h e n u m b e r o f b i t s i n a s i n g l e
l i n e a rt r a c k m e a s u r e d e r u n i t l e n g t h o f t a p e . F o r 9 - t r a c k
p M u l t i v o l u m et a p e f i l e s c a n n o t b e s p e c i f i e do n t h e M o d e l 8 ,
t a p e , t h e 3 4 1 0 / 3 4 11 M a g n e t i cT a p e S u b s y s t e mr e c o r d si n M o d e l 1 0 D i s k S y s t e m ,o r M o d e l 1 2 f o r p r o g r a m st h a t a l s o
d e n s i t i e ro f 8 0 0 o r 1 6 0 0 b p i ( b i t s o r b y t e s p e r i n c h ) . A
s u s et h e B S C A o r d e v i c e s t t a c h e dt o t h e S I O C .
a
d u a l d e n s i t y f e a t u r e i s a v a i l a b l e h a t p e r m i t so p e r a t i o na t
t
e i t h e r i 0 0o r 1 6 0 0 b p i . F o r 7 - t r a c k t a p e , d e n s i t i e s a n b e
c S i m i l a r l y ,f i l e s i n a m u l t i f i l e v o l u m e m u s t b e c o n s i s t e n t .
200, 556, or 800 bpi.
T h a t i s ,a l l f i l e s o n t h e v o l u m em u s t b e l a b e l e d r a l l m u s t
o
b e u n l a b e l e d . S e et h e s y s t e mc o n t r o l p r o g r a m m i n gr e f e r e n c e
manual for Model 15 listed in the Preface for more
FILE PROTECTION
informationon multifile tape volumes.
T h e 3 4 1 0 / 3 4 1 1 u s e sa p l a s t i cw r i t e - e n a b l e i n g m o u n t e d o n
r
t h e t a p e r e e lt o p e r m i t w r i t i n g . l f a t a p e i s m o u n t e d w i t h o u t TAPE LABELS
t h e r i n g li n p o s i t i o n ,w r i t i n g c a n n o t o c c u r ; t h e r e f o r e ,t h e
file is protected. S y s t e m / 3f o l l o w s e i t h e r t h e A m e r i c a n N a t i o n a lS t a n d a r d s
I n s t i t u t e( A N S I ) f o r m a g n e t i c t a p ea b e l s o rI B M M a g n e t i c
l
T a p e L a b e l S t a n d a r d s .T h i s p r o v i d e sc o m p a t i b i l i t y w i t h
INTERSYSTEM TAPE EXCHANGE o t h e r s y s t e m s h a t u s ee i t h e r A N S I o r t h e I B M M a g n e t i c
t
T a p e L a b e lS t a n d a r d s .
T a p e sp r o d u c e do n t h e 3 4 1 0 1 3 4 1 a n d a l l o t h e r I B M h a l f -
1
i n c h t a p e u n i t s o p e r a t i n gi n t h e s a m ed e n s i t y a r e i n t e r -
c h a n g e ; r b l e ;u t p u t d a t a p r o d u c e do n o n e s y s t e m ,s u c h a s
o External Labels
,
I the System/37O, can be used as direct input to another
system, such as System/3. You can attach external labelsto the outside of taoe reels
f o r i d e n t i f i c a t i o n . T h e s el a b e l ss h o u l d i n c l u d et h e r e e l ( o r
v o l u m e ) s e r i a ln u m b e r , n a m e o f t h e f i l e , f i l e n u m b e r , d a t e
TAPE FILE FORMATS t h e f i l e w a s c r e a t e d ,n u m b e r o f t h e v o l u m e ( i f a m u l t i -
v o l u m e f i l e ) . a n d o t h e r i n f o r m a t i o n r e q u i r e df o r
Three t'ypesof file formats can be used with the magnetic instalation.
l
tape subsystem:
o S i n g l l ei l e o n a s i n g l ev o l u m e ( r e e l )
f InternalLabels
. S i n g l ef i l e o n s e v e r av o l u m e s ( m u l t i v o l u m ef i l e )
l T h e i n t e r n a ll a b e l s , o l u m e a n d f i l e , a r e w r i t t e n o n t a p e t o
v
|
p r o v i d ea p r o g r a m m e di d e n t i f i c a t i o no f t h e f i l e . F i l e l a b e l s
o S e v e r a f i l e s o n o n e o r m o r e v o l u m e so n t h e M o d e l 1 b
l p r o v i d ea s a f e g u a r d g a i n s tm i s h a n d l i n g i l e s . L a b e l sa r e
a f
I
( m u l t i f i l eo l u m e )
v c h e c k e db y t a p e d a t a m a n a g e m e n t o d e t e r m i n ew h e t h e r
I
t h e r e e l c o n t a i n i n gt h e d e s i r e df i l e h a s b e e n m o u n t e d
b e f o r e a n y p r o c e s s i n g c c u r s . T h u s , f i l e l a b e l se n s u r et h a t
o
the correct reel is used for input, and that no current data
is destroyed on output.
Magnetic apeConcepts
T 3
P a g eo f G C 2 1 - 5 O 4 O - 3
l s s u e d3 0 J u n e 1 9 7 8
By TNL: GN21-5604
V o l u m e l a b e l sf o r l a b e l e dt a p e sa r e w r i t t e n b y t h e S y s t e m / 3 N o n s t a n d a rld b e l s o n t a i n h a t e v eirn f o r m a t i o nh e u s e r
a c w t
T a p e I n i t i a l i z a t i o np r o g r a ma t t h e t i m e a r e e l i s p r e p a r e df o r d e s i r ets i n c l u d e .T h e s e a b e l s a y v a r y i n l e n g t h n df o r -
o l m a
u s e . T h e v o l u m e l a b e l i d e n t i fi e st h e r e e l a n d i s a l w a y st h e m a t a n d a r et h e c o m p l e t e e s p o n s i b i l i oy t h e u s e r . N o n -
r tf
first record in a reel. The information contained in the standard labels not checked System/3
are by tapedata
v o l u m e l a b e l i s c h e c k e db y t a p e d a t a m a n a g e m e n a n d t m a n a g e m e no r i n p u tf i l e s , n dt h e y m a y n o t b e w r i t t e n
ft a
n e v e ra l t e r e dd u r i n g f i l e p r o c e s s i n g . n y a d d i t i o n a l v o l u m e
A f o r o u t p u tf i l e s . F o r E B C D I C n p u tf i l e sw i t h n o n s t a n d a r d
i
l a b e l sa r e i g n o r e db y t a p e d a t a m a n a g e m e n t . labels, first recordon the volumecannotbe an 80-byte
the
r e c o r d e g i n n i nw i t h V O L i ; f o r A S C I Ii n p u tf i l e s i t h
b g w
nonstandard labels, records cannotbe greater than 80 bytes
b e g i n n i n gi t h V O L 1 .
w
B l a n k s p a c ea t t h e b e g i n n i n go f a r e e l o f t a p e t h a t a l l o w s
t h r e a d i n gt a p e t h r o u g h t h e f e e d m e c h a n i s m .
R e fl e c t i v em a r k e r t h a t i n d i c a t e s h e b e g i n n i n go f t h e
t
r e c ord i ngga r e a .
reco r d i n
F i r s t r e c o r d o n t a p e ( w r i t t e n b y t a p e i n i t i a l i z a t i o n ,$ T l N l T )
I t h a t i d e n t i fi e s t h e r e e l .
I
| -ldentifyt l d e n t i f y t h e f i l e ( w r i t t e n b y t h e s y s t e mw h e n t h e d a t a w a s
written)) and always precededata records.
written a
| |
t t
svmborn d i c a t i n gt h e e n d o f
ir t h e l a b e lg r o u p .
| |
r
t
I ---t---
t
r |
l
l Tape
-oad V o l u m e H e a d e r H e a d e rTape Tape T r a i l e r T r a i l e r End
Mark
j l l l
Leader P o i n t Label L a b e l L a b e l Mark Data M a r k L a b e l L a b e l ( T a p e of
'l (
2 1 2 Reel
) Mark
=--..._--// +
- - L a b e l e dT a p e
rl
F i x e d o r v a r i a b l e - l e n g t a n d b l o c k e d o r u n b l o c k e dd a t a
h
records.
Symbol indicating the end of data records.
End-of-volume or end-of-file labels.
These two tape marks indicate the end of a volume. (There re
i s o n e t a p e m a r k i f t r a i l e r l a b e l sc o n t a i n e n d - o f - v o l u m e a be l lss.)
l le
Reflectivemarkerthat i n d i c a t e s h e e n d o f u s a b l et a p e o n
t
a reel.
Figure 1. Tape Formats: LabeledSingleor MultivolumeFiles
Trailer
Label
2
lVote; Two successive marksindicate end of the
taoe the
p r e v i o utsr a i l e rl a b e l s r e T r a l er T r ai l e r
i
l a s tf i l e o n t h e r e e lu n l e s t h e
s a
Label Label
e n d - o f - v o l u mie ;w h i c h c a s eo n l y o n e t a p em a r k i s
n ,
1 2
p r e s e n t . e f e r o F i g u r e1 f o r t e r m i n o l o g d e f i n i t i o n s .
R t y
o Figure 2. Tape Formats: Labeled Multifile Volume
'
Optional; present, is ignored.
if it
t h e e n d o f t h e l a s tv o l u m e o f a m u l t i v o l u m e
N o t e : T w o t a p e m a r k s a r e w r i t t e n a t t h e e n d o f a s i n g l ev o l u m e f i l e a n d a t
f i l e . O t h e r v o l u m e so f a m u l t i v o l u m e f i l e h a v e o n e t a p e m a r k a t t h e e n d . R e f e rt o F i g u r e 1 f o r t e r m i n o l o g yd e fi n i t i o n s .
o Files
Single Multivolume
Figure Unlabeled
3. or
'
Optional; Present, is ignored'
if it
the volume is multivolumefile, in which
l V o t e ; T w o t a p e m a r k s i n d i c a t et h e e n d o f t h e v o l u m e u n l e s st h e l a s t f i l e o n
c a s e , n l y o n e r a p e m a r k i s p r e s e n t . R e f e rt o F i g u r e
o 1 f o r t e r m i n o l o g y d e fi n i t i o n s '
o MultifileVolume
Figure TapeFormats:Unlabeled
4.
U s e r - s t a n d a r ld b e l sa r e f i l e l a b e l st h a t f o l l o w s t a n d a r d
a F i l e l a b e l sa r e w r i t t e n b e f o r e a n d a f t e r t h e l o g i c a lf i l e o n a
h e a d e ra n c lt r a i l e r l a b e l c o n v e n t i o n s( A N S I o r I B M ) . T h e y r e e l . T h e s el a b e l sa r e r e f e r r e dt o a s f i l e h e a d e rl a b e l so r f i l e
a r e a v a r i a t i o no f s t a n d a r dl a b e l s i t h a p a r t i a l l y f i x e d f o r -
w t r a i l e r l a b e l s d e p e n d i n go n t h e i r p o s i t i o n a n d u s e . H e a d e r
,
-
m a t . T h e s el a b e l sa r e s o m e t i m e sp r o v i d e db y o t h e r s y s t e m s . l a b e l sp r e c e d et h e d a t a f i l e . T r a i l e r l a b e l sa r e e i t h e r e n d - o f
U s e r - s t a n d a r ld b e l sa r e n o t c h e c k e db y S y s t e m / 3 t a p e
a f i l e o r e n d - o f - v o l u m e .E n d - o f - fi l e t r a i l e r l a b e l sa r e w r t t t e n
data managementand may not be written as part of the a t t h e e n d o f t h e l o g i c a lf i l e . E n d - o f- v o l u m et r a i l e r l a b e l s
l a b e lg r o u p . a r e w r i t t e n a t t h e e n d o f a r e e l i n d i c a t i n gt h a t t h e f i l e i s
c o n t i n u e d o n a n o t h e r r e e l . T h e l a b e lf o r m a t s a r e s h o w n
in Appendix A, TaPe Label Formats.
M a g n t : t r cT a p e C o n c e P t s
T A P E R E C O R DA T T R I B U T E S
F : i l e s o n s i s to f a c o l l e c t i o no f l o g i c a lr e c o r d s . T h e
c logical
r e c o r d i s t h e b a s i cu n i t o f i n f o r m a t i o n f o r a p r o g r a m .
The
l o g i c a lr e c o r d sa r e e i t h e r f i x e d o r v a r i a b l el e n g t h .
FrixedLength Records
F i x e d l e n g t h r e c o r d sh a v e a c o n s t a n t n u m b e r o f c h a r a c t e r s
w i t h i n a r e c o r d . T h e r e c o r d sc a n b e e i t h e r b l o c k e d
or
unblocked.
Variable Length Records
V a r i a b l el e n g t h r e c o r d sh a v ea d i f f e r e n t n u m b e r o f
c h a r a c t e r s i t h i n e a c h r e c o r d . T h e r e c o r d sc a n a l s o b e
w
e i t h e rb l o c k e d o r u n b l o c k e d . T h e f i r s t f o u r b y t e s o f t h e
l o g i c a lr e c o r d c o n t a i n t h e l e n g t h o f t h a t r e c o r d . V a r i a b l e
I l e n g t h r e c o r d sc a n n o t b e u s e dw i t h t h e M o d e l 1 0 C a r d
I System.
TAPE BLOCKING FACTORS
R e c o r d st h a t a r e n o t g r o u p e da r e u n b l o c k e d ;t h a t i s . e a c h
r e c o r d m a k e su p a p h y s i c a lb l o c k . B l o c k i n g t h e r e c o r d si s
t h e p r o c e s s f c o m b i n i n g t w o o r m o r e l o g i c a lr e c o r d sb e _
o
f o r e t h e y a r e w r i t t e n o n t a p e . R e c o r d sa r e p r o c e s s e d y
b
t h e s y s t e m i n e i t h e r t h e b l o c k e d o r u n b l o c k e df o r m a t . T h e
s y s t e mh a n c l l e sh e b l o c k i n g a n d d e b l o c k i n go f l o g i c a l
t
r e c o r d ss o y o u n e e d t o d e t e r m i n eo n l y t h e m o s t e f f i c i e n t
b l o c k s i z ef o r t h e f i l e .
R r : c o r d s r p h y s i c a lb l o c k s a r e s e p a r a t e d n t a p e b y a n
o o
I B G ( i n t e r b l o c kg a p ) . T h e s y s t e mp r o d u c e st h i s g a p d u r i n g
tapewrite operations.
Logical Unblocked Records
Ft etock*l [*1 Btoct*l f*1 atocr*l
L o g ic aI Logical LogicaI
IBG IBG
Re c o r d Record Record
Logical Blocked Records
[-i Btock--------{
Log icaI Logical
Record Record
Page GC21
of -5040-3
lssued June
30 1978
B yT N L : G N 2 1 - 5 6 0 4
The numberof logicalrecords combinedinto one physical A S C I IF i l e s
recordor bloc* is the blockingfactor. lf you specifyan
appropriateblockingfactor for an application, many of the A S C I I i s a 7 - b i tc o d ec o n t a i n i n g 2 8 c h a r a c t e r s . S C I I
1 A
interblockgapsareeliminated, the eff iciencyof proc-
and filesarespecif on a FILE control statement
ied (see Control
essing improved.
is Statement Requirements). Whentranslating ASCII files,
an entirerecordis translated witfrout f ielddifferentiation'
Blockingimproves effective the processing speed re- by T h e i n p u tf i l e sa r et r a n s l a t etd E B C D I C r o m A S C I Ib y
o f
ducingthe numberof l/O operations required process
to a tapedata management. the output filesaretranslated
and
file. For example, 30 unblocked
if records werewritten on f r o m E B C D I C o A S C I Ib e f o r eb e i n g r i t t e n . L a b e l s n
t w o
tape.30 write operations would be required.By specifying tapefileswhich containASCII data must conformto the
a b l o c k i n g a c t o ro f 1 0 ,o n l y t h r e ew r i t e o p e r a t i o na r e
f s ANSIformat.
required.The block lengthmust be specified multiples in
of the logicalrecordlength. Your selection the block of
lengthis based the amountof main storage
on available EBCDIC iles
F
(greater tapeefficiencyis obtained with larger blocks) .
EBCDICis an 8-bit codecontaining 256 characters. lf
Approximately 40,000System/3 cards(20 boxes)punched r e q u i r e m e no r A S C I Id a t ai n t e r -
t h e r ei s n o i n s t a l l a t i o n ft
in all 96 columnsmay be contained 2400 feet of tapeif in change, magnetic tapefilesshouldbe recorded EBCDIC; in
t h e d a t ai s w r i t t e ni n t h e 1 6 0 0b p i u n b l o c k e do r m a t . l f a
f EBCDIC is the naturalcoderepresentation the System/3 for
blockingfactor of 10 werespecified, approximately 224,OOO processing unit. The useof EBCDICeliminates object the
c a r d s 1 1 2b o x e s ) o u l db e s t o r e d n t h e s a m e m o u n to f
( c o a program overhead which results from the translation of
t a p eu s i n g h e s a m e e n s i t y .
t d ASCII to EBCDIC.
TAPE CHARACTERCODES
T h e s y s t e m s c a p a b l e f h a n d l i n ga p ed a t af i l e si n o n eo f
i o t
t w o c o d e s :E B C D I C( e x t e n d e b i n a r yc o d e d e c i m a l
d d
i n t e r c h a n gc o d e )o r A S C I I ( A m e r i c a n a t i o n aS t a n d a r d
e N l
C o d ef o r I n f o r m a t i o n n t e r c h a n g eT.h e f o l l o w i n gl i s t s h o w s
I )
the tape formatssupported System/3 the tapedata
by for
files. (Variable lengthrecords not supported the
are by
Model 10 CardSystem.)
F i x e dl e n g t hr e c o r d s :
Blocked r unblocked
o
E B C D I C r A S C I Ic o d e
o
V a r i a b l ee n g t hr e c o r d s :
l
Btocked unblocked
or
E B C D I C o d e( F o r m a tV )
c
ASC|lcode FormaD) ( t
Magnetic Tape Concepts 7
Chapter3. MagneticTape SystemSupport
System/3 program supportprovides input and output capa_ il/lodel8, Model 10 Disk System, Model 12, and Model 15
b i l i t y f o r d a t as t o r a g ei l e s . T h e F I L E s t a t e m e n t .
f which
d e f i n e sh e ' t a p e i l e ,a n d t h e t a p eu t i l i t y p r o g r a m s
t f are A set of OCI- statements must be supplied for each program
d e s c r i b e id t h i s c h a p t e r .
n run. Within this set of statementssthe FILE staremenr i
w h i c h p r o v i d e st h e s y s t e mw i t h i n f o r m a t i o n a b o u t t h e
tapefiles. The formatscf the statements re illustrated a
CONTROL TATEMENT EOUI EMENTS
S R R u s i n gt h e c o n v e n t i o n ss h o w n i n F i g u r eb .
Model 10 CardSystem
; , 1F I L E i i s t o f p a r a m e t e r s
lt '/Loc J +- |
J
= {orr{ , j
Y o u r n u s t s u p p l y o n e F I L E s t a t e m e n tf o r e a c h n e w r a o e
f i i e c r e a t e db y y o u r p r o g r a ma n d f o r e a c ho f t h e e x r s l n g
The LOG control card indicates hetheryou w wanr the F ILE t a p e f i l e s v o u r p r o g r a m u s e s . T h e p a r a m e t e r s l l o w e c jo n
c a r d sa n d d i a g n o s t i cm e s s a g ep r i n t e d . T h e f o r m a r a
s ot the i h e F I L E s t a t e m e n ta r e s h o w n i n F i g u r e6 . T h e k e y w o r d
c a r c ji s i l l u s t r a t e du s i n gt h e c o n v e n t r o n s h o w n i n
s F i g u r e5 . p a r a m e t e r s a y b e i i s t e d o n t h e F I L E s t a t e m e n ti n a n v
m
Drder.
l r t h e L O G c a r d i s n o t u s e d ,t h e F I L E c a r d s ,d i a g n o s t i c
r i e s s a g e s , n r JR U N c a r d sw i l l b e p n n t e d a s i f L O G O N
a
t j e n e r a lc o c i i n gr u l e sf o r t h e F I L E s t a t e m e n ta r e c o n { a t n e e
w a s s p e c r f i e c i T h e L O G c o n t r o i c a r d p r e c e c i ets e F I L E
. h
; n t h e S C F p u b l r c a t r o n si s t e t l i n t h e P r e r a c e .
l
re ro s.
\ , 'I F I L . E l i s t o f p a r a m e r e r s
. \ F I L E c o n t r o l c a r d c o n t a i n si n f o r m a t i o n c o n c e r n r n g
rne
t a p ef i l e s . : / o u m u s t s u p p l y o n e F t L E c a r d f o r e a c nn e w
t a p e t i l e c r e a t e db y y o u r p r o g r a r na n d t o r e a c h o f t h e
t :x i s t i n g l a p e f i l e t h a t V o u r D r o g r a m s s e .
u
T h e p a r a m e t e r s h a r a r e a i i o w e do n t h e c o n t r g i c a r u { l r e
t
s h o w n i n F r , ; u r e6 . T h e x e v w o r d o a r a m e t e ! ..s a v o e r r s t e d
n
, f , nt h e c o n t r o t c a r d i n a n V o r d e r . G e n e r a lc o d r n r ,r;u i e sf o r
the F I LE card are contarned in the iBM System,/3Card
Svstem tlper,etor s Guicte GC2l 7513
A RUN controi card must follow the lasrtrlLE ccntrol
card. This cardserveso detimtt the end of Ihe controi
r
i:ard specificationsanci requeststhat the tape program be
executed. Vlodei i0 Card Svsler.rt control csrds are up.
ward cornpat.iblewrttr tn{ise Df 1.he
itther SVstenr;'3
morlets
P a g eo f G C 2 l - 5 0 4 0 - 3