DB2: How to Save Disk Storage

Two key concepts in DB2 that you always need to remember. The number one is compression and the other one is VARCHAR.

The below post is a summary of difference between these two concepts.

DB2 better disk storage

Even though these are two entirely different “things,” they are each probably done for similar reasons – to save disk storage.

Comparison: Compression Vs VARCHAR

  • With variable columns you always add overhead: there is a two-byte prefix for every VARCHAR column to store the length of the VARCHAR.
  • If instead you use CHAR and turn on compression you no longer need the extra two bytes per row per variable column.
  • All in all, that means that comrpession can return better disk storage savings than variable columns, and all without the programmatic overhead of having to calculate and store the two-byte prefix for each previously variable column.

Author: Srini

Experienced software developer. Skills in Development, Coding, Testing and Debugging. Good Data analytic skills (Data Warehousing and BI). Also skills in Mainframe.