承请各位帮小弟看看，Oracle语句，为何如此慢！多谢

承请各位帮小弟看看，Oracle语句，为何如此慢！谢谢
小弟最近项目遇到一个很棘手的sql，执行的效率特别特比的慢，大约需要6分钟才有结果，请各位帮小弟我看看到底是怎么回事。
    数据库：oracle11g
SQL语句：

select count(*) as col_0_0_
            from ITSM_BP_OVERTIME overtimepr0_     inner join ITSM_BP_INSTANCE overtimepr0_1_
                                                                                                      on overtimepr0_.ID = overtimepr0_1_.ID
        where overtimepr0_1_.JBPM_INSTANCE_ID in
               (select distinct taskinstan3_.PROCINST_
                   from JBPM_POOLEDACTOR pooledacto1_
                   left outer join JBPM_TASKACTORPOOL taskinstan2_ on pooledacto1_.ID_ = taskinstan2_.POOLEDACTOR_
                   left outer join JBPM_TASKINSTANCE taskinstan3_     on taskinstan2_.TASKINSTANCE_ = taskinstan3_.ID_
                where  pooledacto1_.ACTORID_ in
                    ('id:00000000000000000000000000000001',
                      'organization:d5491986b2e144ee9833029d3c390c3d',
                      'role:8a8186a24d654dc5014d994126e869a8',
                      'role:8a8186a24d654dc5014d9940825969a6',
                      'role:8a81bfba4540503b0145407b9ada000d',
                      'role:8a8186a24d654dc5014d9941714a69ad',
                      'role:8a8186a24b06eab5014b0705b940003f',
                      'role:00000000000000000000000000000001',
                      'role:8a81bfb443413cda0143426ba1590043',
                      'role:8a8186a24d654dc5014d9940da0169a7',
                      'role:8a81bfb4437569e601437650631b0028',
                      'role:8a81bfb4461cc90b01461dbcb9150007',
                      'role:8a81bfba4540503b01454075a91f000a',
                      'role:8a81bfba438fa39601438fc384f40001',
                      'role:8a8a18d12d64e5ef012d650ee61c000e',
                      'role:8a8186a24d654dc5014d9941cbee69ae',
                      'role:8a8186a24d654dc5014d99425ae369b0',
                      'role:8a81bfba438fa39601438fc46bf40002',
                      'role:8a81bfba4540503b01454067b39f0004',
                      'role:8a81bfba4540503b01454066610f0003',
                      'role:8a8186a24d654dc5014d9942169669af')   
                   and taskinstan3_.ISOPEN_ = 1
                   and (taskinstan3_.ACTORID_ is null)
                   and taskinstan3_.ISSUSPENDED_ <> 1)
测试描述：
  1、当不使用统计的‘count(*) as col_0_0_’变为'*'就比较快；
  2、单独查询子查询也非常的快；
  3、将子查询的结果直接替换子查询的sql ，效率也很快；
问题点：
  如何将执行效率变得很快？最好能控制到3秒内。求各位帮帮小弟。谢谢啦，来着都有分送哈。
------解决思路----------------------
看看能不能把前一个in换成exists试试呢，一般in会慢一些
------解决思路----------------------
试试这个SQL：

select count(*) as col_0_0_

 from ITSM_BP_OVERTIME IBO     

inner join ITSM_BP_INSTANCE IBI on IBO.ID = IBI.ID

where exists(select 1

               from JBPM_POOLEDACTOR JPR

               left join JBPM_TASKACTORPOOL JTL on JPR.ID_ = JTL.POOLEDACTOR_

               left join JBPM_TASKINSTANCE JTE on JTL.TASKINSTANCE_ = JTE.ID_

             where JTE.ISOPEN_ = 1

               and JTE.ACTORID_ is null)

               and JTE.ISSUSPENDED_ <> 1

               and JPR.ACTORID_ in

                  ('id:00000000000000000000000000000001',

                      'organization:d5491986b2e144ee9833029d3c390c3d',

                      'role:8a8186a24d654dc5014d994126e869a8',

                      'role:8a8186a24d654dc5014d9940825969a6',

                      'role:8a81bfba4540503b0145407b9ada000d',

                      'role:8a8186a24d654dc5014d9941714a69ad',

                      'role:8a8186a24b06eab5014b0705b940003f',

                      'role:00000000000000000000000000000001',

                      'role:8a81bfb443413cda0143426ba1590043',

                      'role:8a8186a24d654dc5014d9940da0169a7',

                      'role:8a81bfb4437569e601437650631b0028',

                      'role:8a81bfb4461cc90b01461dbcb9150007',

                      'role:8a81bfba4540503b01454075a91f000a',

                      'role:8a81bfba438fa39601438fc384f40001',

                      'role:8a8a18d12d64e5ef012d650ee61c000e',

                      'role:8a8186a24d654dc5014d9941cbee69ae',

                      'role:8a8186a24d654dc5014d99425ae369b0',

                      'role:8a81bfba438fa39601438fc46bf40002',

                      'role:8a81bfba4540503b01454067b39f0004',

                      'role:8a81bfba4540503b01454066610f0003',

                      'role:8a8186a24d654dc5014d9942169669af'

                     )

               and IBI.JBPM_INSTANCE_ID = JTE.PROCINST_ 

            )

------解决思路----------------------

select count(*) as cnt

 from ITSM_BP_OVERTIME IBO     

inner join ITSM_BP_INSTANCE IBI on IBO.ID = IBI.ID

where exists(select 1

               from JBPM_POOLEDACTOR JPR

               left join JBPM_TASKACTORPOOL JTL on JPR.ID_ = JTL.POOLEDACTOR_

               left join JBPM_TASKINSTANCE JTE on JTL.TASKINSTANCE_ = JTE.ID_

              where JTE.ISOPEN_ = 1

                and JTE.ACTORID_ is null

                and JTE.ISSUSPENDED_ <> 1

                and JPR.ACTORID_ in

                  ('id:00000000000000000000000000000001',

                      'organization:d5491986b2e144ee9833029d3c390c3d',

                      'role:8a8186a24d654dc5014d994126e869a8',

                      'role:8a8186a24d654dc5014d9940825969a6',

                      'role:8a81bfba4540503b0145407b9ada000d',

                      'role:8a8186a24d654dc5014d9941714a69ad',

                      'role:8a8186a24b06eab5014b0705b940003f',

                      'role:00000000000000000000000000000001',

                      'role:8a81bfb443413cda0143426ba1590043',

                      'role:8a8186a24d654dc5014d9940da0169a7',

                      'role:8a81bfb4437569e601437650631b0028',

                      'role:8a81bfb4461cc90b01461dbcb9150007',

                      'role:8a81bfba4540503b01454075a91f000a',

                      'role:8a81bfba438fa39601438fc384f40001',

                      'role:8a8a18d12d64e5ef012d650ee61c000e',

                      'role:8a8186a24d654dc5014d9941cbee69ae',

                      'role:8a8186a24d654dc5014d99425ae369b0',

                      'role:8a81bfba438fa39601438fc46bf40002',

                      'role:8a81bfba4540503b01454067b39f0004',

                      'role:8a81bfba4540503b01454066610f0003',

                      'role:8a8186a24d654dc5014d9942169669af'

                     )

               and IBI.JBPM_INSTANCE_ID = JTE.PROCINST_ 

            )