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BAJJI
New User
Joined: 15 Jul 2005
Posts: 47
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Hello friendz
Can anyone provide me some good material/manual for IAM-files
or
Can anyone share some knowledge about it if any of you have worked on it.
thanks. |
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BAJJI
New User
Joined: 15 Jul 2005
Posts: 47
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just want to share with u all some info on IAM files, since nothing on this has been posted previously in our forum...
IAM vs. VSAM:
A Comparison of Data Access Methods
By Harry L. Kirkpatrick
Innovation Data Processing's Innovation Access Method (IAM) is a high-performance, indexed access method for OS/390 and MVS/ESA operating systems, which offers advantages over the IBM?-provided Virtual Storage Access Method (VSAM). Existing as non-VSAM data sets provides IAM with capabilities to eliminate the 4.3-gigabyte file-size restriction in VSAM prior to DFSMS V1.3, and to choose a block size that optimizes space utilization on DASD.
This article touches on the strengths and weaknesses of both products. It should be noted that BMC Software's RECOVERY UTILITY (RU? ) for VSAM supports both IAM and VSAM files.
What is IAM?
IAM, as noted previously, offers numerous advantages over the IBM-provided VSAM access method. IAM files exist on DASD as non-VSAM data sets, with IAM providing a VSAM-compatible Application Programming Interface (API) for key-sequenced data sets (KSDS) and entry-sequenced data sets (ESDS) file types and any associated alternate indexes.
Existing as non-VSAM data sets provides IAM with capabilities to eliminate the 4.3-gigabyte file-size restriction in VSAM prior to DFSMS V1.3, and to choose a block size that optimizes space utilization on each of the different type of DASD devices and architectures available. Along with IAM's unique file structure and IAM's Data Compression feature, user data stored in an IAM file typically requires substantially less DASD space than when stored in a VSAM cluster.
The maximum size of an IAM file is determined by a set of limitations imposed by DFSMS, MVS and the architecture of the DASD devices. IAM's file-size limitation, based on the IBM 3390 DASD architecture, is approximately 201 gigabytes of compressed user data.
IAM has been in the MVS marketplace for more than 20 years, providing an outstanding level of performance compared to VSAM. IAM offers CPU time savings, along with reductions in EXCPs that result in reduced elapsed times for batch jobs and improved response times for online systems. In the past few years, the most important features of IAM, for many customers, have been IAM's ability to support VSAM data sets that have exceeded 4.3 gigabytes in size and the DASD space savings of IAM's data compression.
What is VSAM?
VSAM is a high-performance access method used in MVS, OS/390 and VSE/ESA operating systems. Although more than 30 years old, IBM's VSAM remains popular because of its simplicity and high performance. Installations have been using VSAM data sets to hold more and more of their data to the point where many have reached the 4-gigabyte architectural limit for the size of VSAM data sets. This has been particularly true for users of KSDSs, as determined by several surveys conducted worldwide. IBM has recently enhanced VSAM to support record-level sharing and file sizes larger than 4 gigabytes.
The new architectural limit varies according to the size of the data control interval (CI). For a 512-byte CI size, the maximum size is 2 terabytes; for a KSDS with a data CI size of 32 kilobytes, the maximum size is 128 terabytes.
for more info, refer
www.bmc.com/technews/003/IAMvsVSAM.html |
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himanshupant
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Joined: 21 Mar 2007
Posts: 46
Location: India
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| Can someone give a sample JCL on how to define IAM files ? |
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Escapa
Senior Member
Joined: 16 Feb 2007
Posts: 1399
Location: IL, USA
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expat
Global Moderator
Joined: 14 Mar 2007
Posts: 8797
Location: Welsh Wales
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| himanshupant wrote: |
| Can someone give a sample JCL on how to define IAM files ? |
Do you have IAM installed at your site |
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himanshupant
New User
Joined: 21 Mar 2007
Posts: 46
Location: India
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Yes apparently we have IAM installed at our location..
Found out a pretty weird thing about IAM. If I try to NDM an IAM from Production mainframe to Development mainframe , its attributes are getting lost i.e. getting transferred as VSAM ( along with . DATA and .INDEX components) which were not there at Production mainframe for this source file. |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006
Posts: 19244
Location: Inside the Matrix
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Hello,
Suggest you study the IAM material before attempting to do things with an IAM file. . . |
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himanshupant
New User
Joined: 21 Mar 2007
Posts: 46
Location: India
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| Can you please point me to some good IAM materia ? I googled and could not find any good material besides the sites webpage .. |
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Terry Heinze
JCL Moderator
Joined: 14 Jul 2008
Posts: 1249
Location: Richfield, MN, USA
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| Since you've implied that your shop is licensed for IAM, all the relevant documentation (which is copyrighted) should be provided by the vendor and be made available at your site. |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006
Posts: 19244
Location: Inside the Matrix
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JJXANTONY
New User
Joined: 12 Mar 2010
Posts: 3
Location: Chennai
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Hope the below site has the detailed information about how VSAM file can be converted to IAM and how it helps to improve the perfomance of the jobs which use the VSAM files.
jjxblog4mainframe.blogspot.com/ |
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