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Using VSAM with C/C++ for z/OS

 
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rameshvs
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PostPosted: Fri Aug 17, 2007 10:45 pm    Post subject: Using VSAM with C/C++ for z/OS
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Hi,

We have a requirement where we are planning to work with VSAM files for vey large data in the order of millions. We have to use the VSAM with C++ for z/OS. When I am going through some forums came across this statement

VSAM Data Sets with Extended Addressability (>=4GB) are not supported in z/OS C/C++ I/O. (http://ulita.ms.mff.cuni.cz/pub/predn/swi119/C++/cbcpg150.pdf)

Can anyone who has more knowledge about this throw more light on the topic, and how to optimize the usage of space.

Thanks
Ramesh.
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rameshvs
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PostPosted: Wed Aug 22, 2007 6:18 pm    Post subject:
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Hi All..

Finally I found something important for this question through some reading. Here is the text

The following text was taken from the z/OS V1R7.0 XL C/C++ Programming Guide book.

2.11.1 VSAM types (data set organization)


There are three types of VSAM data sets supported by z/OS XL C/C++, all of which are held on direct-access storage devices.

Key-Sequenced Data Set (KSDS) is used when a record is accessed through a key field within the record (for example, an employee directory file where the employee number can be used to access the record). KSDS also supports sequential access. Each record in a KSDS must have a unique key value.
Entry-Sequenced Data Set (ESDS) is used for data that is primarily accessed in the order it was created (or the reverse order). It supports direct access by Relative Byte Address (RBA), and sequential access.
Relative Record Data Set (RRDS) is used for data in which each item has a particular number, and the relevant record is accessed by that number (for example, a telephone system with a record associated with each number). It supports direct access by Relative Record Number (RRN), and sequential access.
In addition to the primary VSAM access described above, for KSDS and ESDS, there is also direct access by one or more additional key fields within each record. These additional keys can be unique or nonunique; they are called an alternate index (AIX).
Notes:

1. VSAM Linear Data Sets are not supported in z/OS XL C/C++ I/O.
2. VSAM Data Sets with Extended Addressability (>=4GB) are not supported in z/OS XL C/C++ I/O.

The following text was taken from the z/OS V1R8.0 C/C++ Programming Guide book.
2.11.1 VSAM types (data set organization)

There are three types of VSAM data sets supported by z/OS XL C/C++, all of which are held on direct-access storage devices.

Key-Sequenced Data Set (KSDS) is used when a record is accessed through a key field within the record (for example, an employee directory file where the employee number can be used to access the record). KSDS also supports sequential access. Each record in a KSDS must have a unique key value.
Entry-Sequenced Data Set (ESDS) is used for data that is primarily accessed in the order it was created (or the reverse order). It supports direct access by Relative Byte Address (RBA), and sequential access.
Relative Record Data Set (RRDS) is used for data in which each item has a particular number, and the relevant record is accessed by that number (for example, a telephone system with a record associated with each number). It supports direct access by Relative Record Number (RRN), and sequential access.
In addition to the primary VSAM access described above, for KSDS and ESDS, there is also direct access by one or more additional key fields within each record. These additional keys can be unique or nonunique; they are called an alternate index (AIX).
Notes:

1. VSAM Linear Data Sets are not supported in z/OS XL C/C++ I/O.

| 2. z/OS XL C/C++ supports extended addressable KSDS, ESDS, and RRDS data
| sets, but does not support extended addressable KSDS and ESDS
| alternate indexes.

Thanks!
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