Suprising output in v$sqlarea

Question

{\code\}
SQL> show parameter cursor
NAME TYPE VALUE
cursor_sharing string SIMILAR
cursor_space_for_time boolean FALSE
open_cursors integer 300
session_cached_cursors integer 20
SQL> show parameter optimizer_dynamic_sampling
NAME TYPE VALUE
optimizer_dynamic_sampling integer 2
SQL> alter session set nls_language=american;
Session altered.
SQL> alter system flush shared_pool;
System altered.
SQL> select hash_value,sql_text,version_count from v$sqlarea
2 where sql_text like 'select count(*) from k%';
no rows selected
SQL> select count(*) from k where id=1;
COUNT(*)
1
SQL> select count(*) from k where id=2;
COUNT(*)
51806
SQL> select hash_value,sql_text,version_count from v$sqlarea
2 where sql_text like 'select count(*) from k%';
HASH_VALUE
SQL_TEXT
VERSION_COUNT
2570880302
select count(*) from k where id=:"SYS_B_0"
2
2570880302
select count(*) from k where id=:"SYS_B_0"
2
HASH_VALUE
SQL_TEXT
VERSION_COUNT
SQL> select count(*) from k where id=3;
COUNT(*)
0
SQL> select hash_value,sql_text,version_count from v$sqlarea
2 where sql_text like 'select count(*) from k%';
HASH_VALUE
SQL_TEXT
VERSION_COUNT
2570880302
select count(*) from k where id=:"SYS_B_0"
3
2570880302
select count(*) from k where id=:"SYS_B_0"
3
HASH_VALUE
SQL_TEXT
VERSION_COUNT
{\code\}
why has two lines in v$sqlarea ????
Edited by: jinyu on Oct 6, 2008 1:41 AM
Edited by: jinyu on Oct 6, 2008 1:43 AM

Answer 1

I guess you have't understood Heman't reply. Similar is an intelligent parameter. It won't just go and pick the cached cursor. Rather than it would check that with a different bind value, do you need to reuse the same cursor or Oracle should create a new one? In your case,though the values are different, 1 & 2 but Oracle is not deeming them for being safe to be shared so its creating multiple cursors.
That's the basic difference of Force and Similar. Force goes for sort of,one-plan-fits-all where as Similar goes for , share-when-safe.
HTH
Aman....