CURSOR_SHARING = exact VS CURSOR

CURSOR_SHARING = exact VS CURSOR_SHARING = EXACT
We are running Oracle 10.2.0.4 with the compatible parameter of 9.2.0.5. My question is fairly simple - does Oracle require parameters to be in uppercase or can they be in lowercase?

Most of our business users are reporting slow response time. Among other observations which are being investigated, it appears that users are often in a wait state for a specified cursor which seems to indicate that cursors are being shared. The application, as it comes from the vendor - all of the cursors are defined as CURSOR_SHARING = SIMILAR. In the ora.init CURSOR_SHARING is set to exact and DEFAULT indicates NO. Does it matter that exact is in lowercase?

Any insight would be much appreciated