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anand tr
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Joined: 12 Aug 2008 Posts: 41 Location: chennai
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What are GSAM and QSAM accessing methods? How do they differ from VSAM? |
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Escapa
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Joined: 16 Feb 2007 Posts: 1399 Location: IL, USA
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Anuj Dhawan
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Joined: 22 Apr 2006 Posts: 6250 Location: Mumbai, India
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Hi,
Further, In IBM mainframe OS, a queued sequential access method (QSAM) is one of the access methods for files. QSAM files are unkeyed, with the records placed one after another, according to entry order. A program can process these files only sequentially, retrieving (with the READ statement or GET macro instruction) records in the same order as they are in the file. Each record is placed after the preceding record.
QSAM files can be on tape, direct access storage devices (DASDs), unit-record devices, and terminals. QSAM processing is best for tables and intermediate storage.
From COBOL point of view, to process QSAM files in a program, a programmer could use COBOL language statements that identify and describe the QSAM files in the ENVIRONMENT DIVISION and the DATA DIVISION.
After a record is created, its length or its position in the file cannot be changed, and it cannot be deleted. QSAM files can, however, be updated on DASD (using REWRITE). The record definitions that are coded in COBOL program and the length of the variables read into and written from determines the amount of data transferred. |
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Young zhang
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Joined: 13 Jun 2008 Posts: 15 Location: china
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Oh!! hi guys, this is a good question!! I will learn it a lot. |
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Anuj Dhawan
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Joined: 22 Apr 2006 Posts: 6250 Location: Mumbai, India
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006 Posts: 6250 Location: Mumbai, India
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Hi Young,
Young zhang wrote: |
Oh!! hi guys, this is a good question!! I will learn it a lot. |
Just surf aroung the forum a little, you will find many more such threads..enjoy being one of the learner of Mainframes.. |
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Young zhang
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Joined: 13 Jun 2008 Posts: 15 Location: china
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Anuj D. wrote: |
Hi Young,
Young zhang wrote: |
Oh!! hi guys, this is a good question!! I will learn it a lot. |
Just surf aroung the forum a little, you will find many more such threads..enjoy being one of the learner of Mainframes.. |
Yes. |
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