Your code must be correct code that conforms to the rules of PL/I. The Enterprise PL/I compiler may produce different results (including abends) than the old compiler for code that is incorrect. You may get "lucky" in that some incorrect code does what you intended, but you must not rely on this. You must change your incorrect code.
These rules may seem obvious: for example, no user would expect to write to an element of an array using an index that is outside of the bounds of that array. However, in some cases, the fact that code is incorrect and needs to be changed may be less obvious. This section will attempt to describe some instances of incorrect code that must be changed; however, it is not a list of all incorrect code since the opportunities for writing bad code are endless.