When "cursor: pin S wait on X" wait event is signficant in the "Top Waits" section of AWR, then investigate the number of cursors that you have on the system.

As the AWR report starts reporting on any Version Count > 20; it is a good indicator of a potential performance issue.

Version counts in to the hundreds and thousands can be catastrophic and these cases need to be examined and the numers reduced.

Oracle says - in MOS DOC ID 296377.1 - that high version counts are expected and they are not a result of any defect