Dear youth,
As you are aware, emoluments attached to a work/worker/workman are linked to minimum wages pertaining to the nature of duty grouped as unskilled/semi-skilled/skilled, etc. These minimum wages (MW) are divided into two parts - basic and DA. In some sectors, these are further divided into Fixed DA (FDA) and Variable DA (vDA). Periodically, central and state governments revise these rates under certain formulas, e.g., Consumer Price Index (CPI) and/or Wholesale Price Index (WPI). The mechanism of how this works is explained in various blogs on the internet which you can search for and learn.
Since DA is revised periodically, say once in a quarter or half-yearly based on the increase or decrease in the indexes of CPI/WPI to which the pattern followed in an establishment is linked. If you indicate any specific sector/state and nature of duty, you will get the query answered in detail. For further information, there are links provided on your side of the screen and bottom, search and use.