Algorithmic Compression
Teradata Database software includes several standard compression algorithms, in the form of UDFs, which you can use to compress many types of data by table column. You can also create custom compression and decompression algorithms in UDF format.
When column values are mostly unique, algorithmic compression (ALC) may provide better compression results than MVC. When columns have repeated values, you can use ALC and MVC concurrently on the same column, but the system does not apply ALC to any value covered by MVC.
ALC generally functions best on cold (seldom used) data because of the amount of CPU required for decompress/recompress when compressed data is accessed, although some ALC algorithms require less CPU than others. ALC is considered to be the most difficult to implement of all the compression methods.
You can use algorithmic compression to compress table columns with the following data types: