Redvers Compression Device
The Redvers Compression Device gives you the ability to reduce memory overheads, carbon emissions and data storage costs without compromising your data assets.
Redvers Consulting have engineered a compression and deduplication algorithm specifically designed to produce optimal data reduction rates for COBOL data. The algorithm is also designed to use minimal computer resources, especially when decompressing, so that archived information can be retrieved on-line with minimal disruption.
Main features:
- Reduced machine memory overhead
- Money saved on DASD hardware
- Faster disk I-O
- Time and space saved when archiving
- Reduced carbon footprint
- Compression rates up to 75%
- Runs on any COBOL platform
- Distributed in COBOL source code (cloaked)
- Fast decompression rate for real-time retrieval
- Works with non-COBOL data too
- Supports calls from batch or on-line
- Free 30 day trial available
As the software is distributed in COBOL source code, it can be compiled and run on IBM mainframe, iSeries/AS400, UNIX, HP, CA-Realia, Siemens, Fujitsu, Micro Focus or any other COBOL platform.
The Redvers Compression Device consists of a pair of simple but efficient COBOL subroutines that compress and decompress data strings as required. These data strings can be single fields, parts of a record, complete records or even a file of records concatenated end-to-end.
Field level compression can be used to leave record keys uncompressed. This gives applications access to the data without the need to decompress the whole file, disk or tape first.
Download a Compression Device PDF white paper here:
How it Works
Compression can be performed in a scheduled procedure that selects the data suitable for compression. This data would then be passed to the Redvers compression routine (RCCMPRES) which returns the string in its compressed form. The compressed string can then be used for fast access while the original data is removed from on-line storage.
Application programs that require the compressed information, would pass the compressed string to the decompression routine (RCUNPRES) which returns the data string in its standard form. No other files or parameters are required.
If the application needs to update compressed information, the updated details can be passed through RCCMPRES and the output rewritten to the compressed data store.
Disk space in databases and indexed files can be saved by rewriting records with key information unchanged but with the majority of the data in its compressed state.
The diagram below shows how a compression / decompression procedure might be used in a typical application environment.
Reduced Carbon Emissions
The following chart shows how 60% compression (case study rate) can produce real power and carbon dioxide savings for DS8000 storage devices.
1 640 additional watts per disk enclosure pair (270W x 2) + (25W x 4) - see "Power consumption and environment" section of IBM System Storage DS8000: Architecture and Implementation
2 0.537Kg per kilowatt-hour - see Carbon Trust Conversion Factors
3 Containing 32 x 15 KRPM, 300GB disks running 7 + P RAID 5 configuration (7.8TB data capacity)
Technical Information
The Redvers Compression Device (2.1) uses a "lossless" compression algorithm designed and developed by Redvers Consulting. This algorithm provides optimum compression rates for COBOL application type data, using minimal computer resources. The algorithm can also be used to compress data not in COBOL format.
The algorithm is not "Huffman" or "arithmetic" based and doesn't require the overhead of building a probability tree and adding it to the compressed string. However, it does use a standard "sliding window" technique for data deduplication.
The size of the "sliding window" can be adjusted by the application to respond to different system priorities: a large window will produce better deduplication ratios but require more CPU time; a small window will result in poorer deduplication ratios but require less CPU time.
As RCCMPRES and RCUNPRES are standard COBOL programs, compiled at the customer's site, any limit on the length of data stings passed, are defined by the limitations of the compiler used.
Compression techniques include:
- Deduplication of repeated characters such as spaces or zeroes
- Application data deduplication (within the "sliding window")
- The breaking down of commonly used characters into shorter bit patterns
- Preserving random bit patterns caused by the presence of binary data fields
Input data can be in the ASCII or EBCDIC character sets.
Actual compression rates range from 35% to 75%, depending on the length of the input data string and the length of the "sliding window".
Compression time is 0.3 megabytes per CPU second (using a "sliding window" of 400 bytes) and decompression is more than 14 megabytes per CPU second. All benchmark timings were performed on an IBM zSeries mainframe running z/OS 1.10.