Ignition offers two different algorithms for pre-compressing the data (trimming unnecessary values). The two algorithms corresponding to the two value mode properties of the tag are: Discrete and Analog.

The value mode (Discrete or Analog) dictates the type of value that the tag represents, affects how the deadband is applied to values, and how interpolation is performed when querying.

• Discrete
  The value uses a simple deadband and is only stored when a new value is + /- the deadband value away from the previously stored value.
  

• Analog
  The deadband is used to form a corridor along the trajectory of the value. A new value is only stored when it falls outside the previous corridor. When this occurs, the trajectory is recalculated and a new corridor is formed.

Typically, Discrete is used for boolean or integers that represent state, and Analog is used for floats or integers that change more often (which is why you want to perform compression).

You choose and set the Value Mode on the History section of the Tag Editor window.

While advanced users can change the table according to their database to be more efficient (for example, using a compressed engine), Ignition does not perform binary compression or encrypt the data in any way.