Interested to Buy Any Domain ? << Click Here >> for more details...
what is the advantage of sync class
- 3 Answers
- 11765 Views
- ACS, I also Faced
- E-Mail Answers
Answers were Sorted based on User's Feedback
Answer / rajini
The SYNCHRONIZED clause is sometimes used with USAGE IS
COMP or USAGE IS INDEX items. It is used to optimize speed
of processing but it does so at the expense of increased
storage requirements.
Many computer memories are organized in such a way that
there are natural addressing boundaries - such as word
boundaries. If no special action is taken some data items
in memory may straddle theses boundaries. This may cause a
processing overhead as the CPU may need two fetch cycles to
retrieve the data from memory.
The SYNCHRONIZED clause is used to explicitly align COMP
and INDEX items along their natural word boundaries.
Without the SYNCHRONIZED clause, data-items are aligned on
byte boundaries.
The word SYNC can be used instead of SYNCHRONIZED.
For the purpose of illustrating how the SYNCHRONIZED clause
works let us assume that a COBOL program is running on a
word-oriented computer where the CPU fetches data from
memory a word at a time.
01 three-byte pic x(3) value 'dog'.
01 two-byte pic s9(4) comp .
In this program we want to perform a calculation on the
number stored in the variable TwoBytes (as declared in the
diagram below). Because of the way the data items have been
declared, the number stored in TwoBytes straddles a word
boundary.
In order to use the number, the CPU has to execute two
fetch cycles - one to get the first part of the number in
Word2 and the second to get the second part of the number
in Word3. This double fetch slows down calculations.
01 three-byte pic x(3) value 'dog'.
01 two-byte pic s9(4) comp sync .
Now consider the impact of using the SYNCHRONIZED clause.
The number in TwoBytes is now aligned along the word
boundary, so the CPU only has to do one fetch cycle to
retrieve the number from memory. This speeds up processing
but at the expense of wasting some storage (the second byte
of Word2 is no longer used).
| Is This Answer Correct ? | 9 Yes | 1 No |
Answer / ch.mohan
access will be fast wether it intraduce some slack bytes
| Is This Answer Correct ? | 3 Yes | 1 No |
Answer / nagaraj ramamoorthy
The purpose of the SYNC clause (when it was introduced) was
to align the data names to the natural machine word
boundaries so that it will be efficient to retrieve data.
This was introduced when the processing speed was very slow
and system was built on word architecture. Modern systems
are quite fast and this does not make significant
difference.
It can be used to numeric and alphanumeric data items. you
can also specify how to align RIGHT/LEFT. if you do not
specify, complier will take the best one that is efficient.
It should be used with 01 and 77 levels and it should not
be used with group items, because compiler will add
bits/bytes in between group items so finding the exact size
will be difficult for the programmer.
| Is This Answer Correct ? | 0 Yes | 1 No |
What does MAXCC 3 means? It is used in one my codes.
What is reference modification? What is UNION in sql and syntax? What is the difference between GDGS and VSAM? Which is prefer one? What is processing groups in endevor?
What is SDSF?
what is sort? whis is internal & external sort ?when do u go for inter sort & external sort? tell about some sort utilites?
What is the difference between goback, stop run and exit program in cobol?
What are VS COBOL 11 special features?
How to read records in reverse order in flat file? I know we can do it by reading all records into an array.... Then read records in reverse order by using subscript or index but can any body give me the exact code.
i was faced one question- i have value -00001234.56 Suppress the zeroes and the output should be -1234.56 But Not - 1234.56 spaces should not be available after suppressing the zeroes. logic in jcl and cobol?
I have program P1 which calls file F1 which has 100 records and following structure 001 .................. 002 .................. 003 .................. 098 .................... 099 ................... 100 .................... Now I want to read these files and write these records in file F2 in following manner. 001 ...... 051 ..... 002 ...... 052 ..... 003 ...... 053 ..... .......... ....... .......... ....... .......... ....... 048 ........ 098 ...... 049 .......... 099 ....... 050 .... 100 ......
What is Control Break processing ?
How do u find the programs calling the given module, without having doing 3.13 on loadlib/source library?
how to convert the recors form vsam file to db2 table tru file aid
COBOL 
