A CDE Definition
variable length field
A record structure that holds fields of varying lengths. For example, PAT LOPEZ would take nine bytes and GEORGINA ALLISON BARTHOLOMEW would take 28 plus a couple of bytes that define the length of the field. If fixed length fields were used, at least 28 bytes would have to be reserved for both names.
Variable Length Text Fields
Years ago, storage was costly, and variable field lengths were essential. Today, storage is dirt cheap by comparison. However, if there are text elements in a database that vary greatly, variable length fields save a lot of space. In addition, databases in many companies have reached mammoth proportions, and storage savings are welcome.
Variable lengths require more processing, because every field has to be encoded into the variable format before being written to storage. Conversely, after being read back into memory, the variable fields may have to be converted to a fixed length for processing.
The Compression Alternative
The same storage savings is often achieved by using fixed length fields and compressing the data in storage. With text, all contiguous blank bytes are filtered out. See real-time compression.
The ability to compress data before it is written to the hard disk without any noticeable loss in speed compared to non-compressed data. Modern operating systems provide a real-time compression capability for a portion or all of the hard disk, and earlier products such as Stacker and SuperStor were third-party software that added this capability.
Images May Also Be Compressed
GIF images are compressed when they are saved, without any loss of data. JPEG images are also compressed, but eliminate pixels in the process (see lossy compression).
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