Difference in query output after using cursor

Question

can any one help out why the differences are in output, especially the bold and italic ?
SQL> alter session set cursor_sharing='EXACT';
Session altered.
SQL> select '2' from dual;
2
SQL> select 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaa' from dual;
'AAAAAAAAAAAAAAAAAAAAAAAAAAAA
aaaaaaaaaaaaaaaaaaaaaaaaaaaaa
SQL> alter session set cursor_sharing='SIMILAR';
Session altered.
SQL> select '8' from dual;
'8'
8
SQL> select TRIM('8') from dual;
TRIM('8')
8
SQL> select 'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb' from dual;
'BBBBBBBBBBBBBBBBBBBBBBBBBBBBB
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
SQL> select TRIM('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb') from dual;
TRIM('BBBBBBBBBBBBBBBBBBBBBBBB
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
SQL> select TRIM('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb') from dual;
TRIM('BBBBBBBBBBBBBBBBBBBBBBBB
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

Answer 1

oracle support says it best:
When cursor_sharing = exact,
we don't convert the literal into binds and hence we know the actual size of the
format mask. So buffer length is computed and known.
When cursor_sharing = similar / force, the intention is to reuse the cursor for similar types of statements to avoid re-parsing. So the server converts the literal (format mask) into a bind. At this stage we don't know the actual size of the data, and set buffer length to be maximum, however this affects the display of the column header length in SQLPLUS; not the actual data .