Originally, computers used 1 byte (8 bits) to store a character. This
allowed for up to 256 characters, which is plenty for upper and lower case
letters, digits, punctuation, and special characters (space, line feed,
etc.) However, it is not enough for character based languages (such as
Since 2000, Access therefore uses Unicode: 2 bytes per character, which
copes with 65536 characters but takes twice the space to store. For
languages like English, you can use Unicode Compression to reduce the wasted
The issue is not just reducing the number of bytes being used on the hard
disk: large disks are inexpensive. More significant is the time it takes to
read all the data off the drive, or to write the data onto the drive. Since
most databases are disk-bound, it makes sense to use Unicode Compression to
reduce the reads and writes.
Of course, there's no such thing as a free lunch, so when you turn Unicode
Compression on, your CPU must compress the text (during a write) and
decompress it (during a read.)
There are too many factors to give a definitive answer on when a db will
benefit form Unicode Compression, but if we assume you have a fast processor
and ordinary drives and lots of text and not terribly complex data matching
and more reads than writes, my guess is that your application will be
disk-bound and hence Unicode Compression will be useful.
Allen Browne - Microsoft MVP. Perth, Western Australia
Tips for Access users - http://allenbrowne.com/tips.html
Reply to group, rather than allenbrowne at mvps dot org.