With V3R2 of Enterprise PL/I, NORENT became the default (previously RENT was the default). This default will ease your migration because now, by default, the new compiler, just like the old compilers, will not generate any extra code to make your static variables writeable and still REENTRANT (which is what the RENT option does).
Also note that using the RENT option requires the prelinker to be used or your modules to be stored in PDSEs.
The new WRITABLE option is also the default since it gives you the best performance in combination with NORENT.
But if you are using the NORENT option, then you must also use the NOWRITABLE option if both of the following are true:
With Enterprise V3R4, the NOWRITABLE option has two suboptions which can also make your code more (or less) compatible: