绑定变量和非绑定变量的资源消耗对比 首先初始化数据 Create table tsts as select level as col1 ,rdbms_random.string(p,10) as col2 from dual connect by level = 10000 ; create or replace procedure p1 as rec_tsts%rowtype ; begin for i in1 .. 100绑定变量和非绑定变量的资源消耗对比首先初始化数据create table tsts as select level as col1 ,rdbms_random.string(‘p’,10) as col2 from dual connect by level create or replace procedure p1 as rec_tsts%rowtype ;begin for i in1 .. 10000 loop execute immediate 'select * from tsts where col1='||i into rec_ ;end loop;end ;create or replace procedure p2 as rec_tsts%rowtype ;begin for i in1 .. 10000 loop execute immediate 'select * from tsts where col1=:1 ' into rec_ using i;end loop;end ;开始比较（使用tom的runstat脚本）
exec runstats_pkg.rs_start ;exec p1 ;exec runstats_pkg.rs_middle ;exec p2 ;exec runstats_pkg.rs_stop(1000) ;_dexter@FAKE> exec runstats_pkg.rs_start ;PL/SQL procedure successfully completed.
_dexter@FAKE> exec p1 ;PL/SQL procedure successfully completed.
_dexter@FAKE> exec runstats_pkg.rs_middle ;PL/SQL procedure successfully completed.
_dexter@FAKE> exec p2 ;PL/SQL procedure successfully completed.
_dexter@FAKE> exec runstats_pkg.rs_stop(1000);Run1 ran in 1163 cpu hsecs Run2 ran in 64 cpu hsecs run 1 ran in 1817.19% of the time Name Run1 Run2 Diff STAT...recursive cpu usage 1,119 59 -1,060 STAT...DB time 1,150 75 -1,075 STAT...CPU used when call star 1,173 72 -1,101 STAT...CPU used by this sessio 1,172 64 -1,108 STAT...buffer is not pinned co 31,411 30,087 -1,324 STAT...consistent gets 41,986 40,457 -1,529 STAT...consistent gets from ca 41,986 40,457 -1,529 STAT...session logical reads 42,047 40,494 -1,553 STAT...sorts (rows) 1,676 3 -1,673 LATCH.cache buffers chains 66,737 61,883 -4,854 STAT...sql area evicted 9,519 4 -9,515 STAT...session cursor cache hi 360 10,018 9,658 STAT...parse count (hard) 10,053 4 -10,049 STAT...enqueue releases 10,053 4 -10,049 STAT...enqueue requests 10,053 4 -10,049 STAT...parse count (total) 10,057 4 -10,053 LATCH.enqueue hash chains 20,379 110 -20,269 STAT...recursive calls 41,827 10,157 -31,670 LATCH.shared pool simulator 38,862 40 -38,822 LATCH.shared pool 455,526 10,683 -444,843 LATCH.row cache objects 513,487 441 -513,046 STAT...logical read bytes from 344,449,024331,726,848 -12,722,176 Run1 latches total versus runs -- difference andpct Run1 Run2 Diff Pct 1,097,601 74,729 -1,022,872 1,468.78% PL/SQL procedure successfully completed.
分析可以看到资源使用相差是非常巨大的。我们示例中的sql语句是典型的应用在oltp系统中的，可以看到使用绑定变量消耗更少的资源。我们观察相差比较大的事件。执行可以完全肯定，绑定变量优于非绑定变量。主要由于下面几个相差较大的事件影响。
BindingNo bindingDescsession cursor cache hits10,018360cursor命中率sql area evicted49,519Shared pool 不足引起的ageoutparse count (hard)410,053硬解析enqueue releases410,053Enqueue锁释放enqueue requests410,053Enqueue锁请求parse count (total)410,057解析总次数enqueue hash chains11020,379获取hash chain次数recursive calls10,15741,827读取数据字典信息可能引发recursive callsshared pool simulator4038,862Advice信息收集shared pool10,683455,526Shared pool使用row cache objects441513,487硬解析会读取更多的统计信息logical read byte331,726,848344,449,024逻辑读可以看到，因为硬解析，oracle数据库优化器需要重新对语句进行优化操作，需要获取更多的latch并且执行更多的操作，而且对于oltp系统中的语句，优化期间所做的操作甚至比查询数据需要更多的时间，所以在OLTP系统中，更多的使用绑定变量，是非常有必要的。
附录：tom runstat 脚本的使用
1. 创建临时表
create or replace view stats as select 'STAT...' || a.name name, b.value from v$statname a, v$mystat b where a.statistic# = b.statistic#union all select 'LATCH.' || name, gets from v$latch union all select 'STAT...Elapsed Time', hsecs from v$timer;需要授权相应的视图权限grant select on v_$statname to &&username ;grant select on v_$mystat to &&username ;grant select on v_$latch to &&username ;grant select on v_$timer to &&username ;
2. 创建临时表
create global temporary table run_stats ( runid varchar2(15),name varchar2(80),value int ) on commit preserve rows;
3. 创建相应的runstat包
create or replace package runstats_pkg as procedure rs_start;procedure rs_middle;procedure rs_stop(p_difference_threshold in number default 0);end;/ create or replace package body runstats_pkg as g_start number;g_run1 number;g_run2 number;procedure rs_start is begin delete from run_stats;insert into run_stats select 'before', stats.* from stats;g_start := dbms_utility.get_cpu_time;end;procedure rs_middle is begin g_run1 := (dbms_utility.get_cpu_time - g_start);insert into run_stats select 'after 1', stats.* from stats;g_start := dbms_utility.get_cpu_time;end;procedure rs_stop(p_difference_threshold in number default 0) is begin g_run2 := (dbms_utility.get_cpu_time - g_start);dbms_output.put_line('Run1 ran in ' || g_run1 || ' cpu hsecs');dbms_output.put_line('Run2 ran in ' || g_run2 || ' cpu hsecs');if (g_run2 0) then dbms_output.put_line('run 1 ran in ' ||round(g_run1 / g_run2 * 100, 2) ||'% of the time');end if;dbms_output.put_line(chr(9));insert into run_stats select 'after 2', stats.* from stats;dbms_output.put_line(rpad('Name', 30) || lpad('Run1', 12) ||lpad('Run2', 12) || lpad('Diff', 12));for x in (select rpad(a.name, 30) ||to_char(b.value - a.value, '999,999,999') ||to_char(c.value - b.value, '999,999,999') ||to_char(((c.value - b.value) - (b.value - a.value)),'999,999,999') data from run_stats a, run_stats b, run_stats c where a.name = b.name and b.name = c.name and a.runid = 'before'and b.runid = 'after 1'and c.runid = 'after 2'and abs((c.value - b.value) - (b.value - a.value)) >p_difference_threshold order by abs((c.value - b.value) - (b.value - a.value))) loop dbms_output.put_line(x.data);end loop;dbms_output.put_line(chr(9));dbms_output.put_line('Run1 latches total versus runs -- difference and pct');dbms_output.put_line(lpad('Run1', 12) || lpad('Run2', 12) ||lpad('Diff', 12) || lpad('Pct', 10));for x in (select to_char(run1, '999,999,999') ||to_char(run2, '999,999,999') ||to_char(diff, '999,999,999') ||to_char(round(run1 / decode(run2, 0, to_number(0), run2) * 100,2),'99,999.99') || '%' data from (select sum(b.value - a.value) run1,sum(c.value - b.value) run2,sum((c.value - b.value) - (b.value - a.value)) diff from run_stats a, run_stats b, run_stats c where a.name = b.name and b.name = c.name and a.runid = 'before'and b.runid = 'after 1'and c.runid = 'after 2'and a.name like 'LATCH%')) loop dbms_output.put_line(x.data);end loop;end;end;/
4. 用法
exec runstats_pkg.rs_start;p1 exec runstats_pkg.rs_middle;p2 exec runstats_pkg.rs_stop(1000);
示例：
dexter@REPO>exec runstats_pkg.rs_start;PL/SQL 过程已成功完成。
dexter@REPO>delete from t1 ;已删除 1 行。
dexter@REPO>exec runstats_pkg.rs_middle;PL/SQL 过程已成功完成。
dexter@REPO>insert into t1 select level from dual connect by level已创建 10000 行。
dexter@REPO>exec runstats_pkg.rs_stop(100);Run1 ran in 1 cpu hsecs Run2 ran in 4 cpu hsecs run 1 ran in 25% of the time Name Run1 Run2 Diff LATCH.session idle bit 331 207 -124124 STAT...redo entries 15 167 152 LATCH.SQL memory manager worka 1,012 807 -205 STAT...db block changes 77 300 223 LATCH.enqueue hash chains 1,035 794 -241 LATCH.cache buffers chains 2,182 2,425 243 STAT...db block gets 60 304 244 STAT...db block gets from cach 60 304 244 STAT...session logical reads 89 374 285 LATCH.shared pool 1,016 515 -501 STAT...Elapsed Time 4,370 3,681 -689 LATCH.row cache objects 2,063 1,082 -981 STAT...undo change vector size 3,908 29,856 25,948 STAT...physical read bytes 8,192 40,960 32,768 STAT...physical read total byt 8,192 40,960 32,768 STAT...cell physical IO interc 8,192 40,960 32,768 STAT...session uga memory max 123,512 65,488 -58,024 STAT...session uga memory 65,488 0 -65,488 STAT...file io wait time 8,767 113,342 104,575 STAT...redo size 5,220 167,168 161,948 STAT...logical read bytes from 729,088 3,063,808 2,334,720 Run1 latches total versus runs -- difference and pct Run1 Run2 Diff Pct 11,252 8,792 -2,460 127.98% PL/SQL 过程已成功完成。