For those looking to the next upgrade – here’s an early warning from Oracle:
ANNOUNCEMENT: Deprecating the cursor_sharing = ‘SIMILAR’ setting (Doc ID 1169017.1)
“We recommend that customers discontinue setting cursor_sharing = SIMILAR due to the many problematic situations customers have experienced using it. The ability to set this will be removed in version 12 of the Oracle Database (the settings of EXACT and FORCE will remain available). Instead, we recommend the use of Adaptive Cursor Sharing in 11g.”
The rest of the note contains some interesting information about the behaviour and side effects of this option – which may also help you debug some library cache issues if you’re currently running with this value set in 11g.