Moved to 19c and plain PL/SQL loop first execution is slow

Hi!

Recently installed 19c (19.13.0.0.0) and are having performance issues in PL/SQL.

First 1 or 2 executions of a PL/SQL loop is slow, by a factor of 1.5 to 2 - in the same execution context (the same "run").

There is no SQL involved. Only PL/SQL code.

For our web app, which does PL/SQL loops here and there, this adds time to the overall request. Problem did not exist in 12c (12.1.0.2.0).

In 12c, timings: 21 21 23 21 23

in 19c, timings: 38 29 17 18 18

As you can see every loop executes the same in 12c, but first loop(s) are much slower in 19c. Why?

Is there some new PL/SQL "optimizer" that does some magic? If so, can it be disabled?