A relative record data set (RRDS) is a type of
data set A data set (or dataset) is a collection of data. In the case of tabular data, a data set corresponds to one or more database tables, where every column of a table represents a particular variable, and each row corresponds to a given record of the ...
organization used by
IBM's
VSAM Virtual Storage Access Method (VSAM) is an IBM DASD file storage access method, first used in the OS/VS1, OS/VS2 Release 1 (SVS) and Release 2 (MVS) operating systems, later used throughout the Multiple Virtual Storage (MVS) architecture and no ...
computer data storage system.
Records are accessed based on their ordinal position in the file (''relative record number'', RRN).
For example, the desired record to be accessed might be the 42nd record in the file out of 999 total.
The concept of RRDS is similar to
sequential access
Sequential access is a term describing a group of elements (such as data in a memory array or a disk file or on magnetic tape data storage) being accessed in a predetermined, ordered sequence. It is the opposite of random access, the ability to ...
method, but it can access with data in
random access and dynamic access.
Structure
An RRDS consists of data records in sequence, with the record number indicating the record's logical position in the data set.
A program can access records randomly using this positional number or access records sequentially.
But unlike a
Key Sequenced Data Set
A key-sequenced data set (KSDS) is a type of data set used by IBM's VSAM computer data storage system. Each record in a KSDS data file is embedded with a unique key. A KSDS consists of two parts, the data component and a separate index file known ...
, an RRDS has no keys, so the program cannot access records by key value.
See also
*
Key Sequenced Data Set
A key-sequenced data set (KSDS) is a type of data set used by IBM's VSAM computer data storage system. Each record in a KSDS data file is embedded with a unique key. A KSDS consists of two parts, the data component and a separate index file known ...
*
Entry Sequenced Data Set
An entry-sequenced data set (ESDS) is a type of data set used by IBM's VSAM computer data storage system. Records are accessed based on their sequential order, that is, the order in which they were written to the file; which means that accessing ...
*
Linear Data Set
A linear data set (LDS) is a type of data set organization used by IBM's VSAM Virtual Storage Access Method (VSAM) is an IBM DASD file storage access method, first used in the OS/VS1, OS/VS2 Release 1 (SVS) and Release 2 (MVS) operating system ...
References
*https://web.archive.org/web/20051013071230/http://www.jaymoseley.com/hercules/vstutor/vstutor.htm
*http://www.mvsforums.com/techfaqsvsam.html
*https://web.archive.org/web/20070311021954/http://www.redbooks.ibm.com/redbooks/SG246105/wwhelp/wwhimpl/js/html/wwhelp.htm
Computer file systems
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