Example

The amount of information that needs to be entered into the database 
is enormous, and it needs to be entered in a different way for each patient. 
This will make the design process complex."

What's wrong?

The example uses a demonstrative pronoun (such as this, these, or those), but there are two or more possible antecedents. To which does the pronoun refer?

Consider this example:

The new equipment arrived yesterday, and everything is in 
working order. This was something of a surprise.

Which is surprising? The fact that the equipment arrived, or that it was in working order, or both?

How to fix this problem

Supply a clarifying noun:

The new equipment arrived yesterday, and everything is in working order. 
This happy outcome was something of a surprise.