如何减小SQL 的物理读，。
1.dev time：1226 1个跑批
db_file_multiblock_read_count =128
60.05 (mins) 26-Dec-17 16:00:20 ~ 26-Dec-17 17:00:20
每秒81个IO 读，26个IO 写。
Statistic Total per Second per Trans
physical read IO requests 291,800 80.98 543.39
physical write total IO requests 95,521 26.51 177.88
Event Waits Total Wait Time (sec) Wait Avg(ms) % DB time Wait Class
db file scattered read 198,748 714.5 4 44.8 User I/O <- - 198,748次，每个4ms
direct path read temp 51,272 196.7 4 12.3 User I/O
db file sequential read 31,718 90.3 3 5.7 User I/O <- - 31,718 次 ，每个3ms
direct path write temp 43,416 87.7 2 5.5 User I/O
2.prod :time:1226 1个跑批
180.05 (mins) 26-Dec-17 02:00:20 ~ 26-Dec-17 05:00:20
db_file_multiblock_read_count =48
每秒214个IO 读，26个IO 写。
Event Waits Total Wait Time (sec) Wait Avg(ms) % DB time Wait Class
db file scattered read 523,916 2981.7 6 59.5 User I/O <- 523,916次，每个6ms, 这个增长3倍，预期因为db_file_multiblock_read_count 调小了3倍
direct path write temp 53,365 430.7 8 8.6 User I/O
db file sequential read 1,589,363 67.4 0 1.3 User I/O <- 1,589,363次，每个0.04ms,这个增长最多，增长达到50倍
log file sync 1,916 30.1 16 .6 Commit
local write wait 2,075 29.6 14 .6 User I/O
enq: RO - fast object reuse 32 21.5 673 .4 Application
direct path read 105,266 8 0 .2 User I/O
physical read IO requests 2,317,803 214.42 8,307.54
physical write IO requests 279,717 25.88 1,002.57
3.prod :time:1227 1个跑批
每秒214个IO 读，26个IO 写。
180.05 (mins) 27-Dec-17 02:00:27 ~ 27-Dec-17 05:00:27
db_file_multiblock_read_count =48
Top 10 Foreground Events by Total Wait Time
db file scattered read 183,319 4057 22 42.2 User I/O <- 183,319次，每个22ms,这个增长最多，
db file sequential read 1,955,212 3133.5 2 32.6 User I/O <- 1,955,363次，每个2ms,这个增长最多，增长达到50倍
control file sequential read 37,862 45.2 1 .5 System I/O <- 37,862 次，每个1ms,这
physical read IO requests 2,251,103 208.21 7,682.95
physical write IO requests 172,423 15.95 588.47
20171227 solution:
db_file_multiblock_read_count 48 Wait Avg(ms) 6
db_file_multiblock_read_count 128 Wait Avg(ms) 22
#######prod
20171228 solution：
主要消耗资源db file sequential read 为如下SQL:
SQL ID: 3mhmz5nbhgn2q Plan Hash: 4065600310
SELECT TRIM(DBMS_LOB.SUBSTR(WM_CONCAT(DATAVAL))) VALUE FROM (SELECT 'CNT=' || MAX(FLAG) AS DATAVAL FROM (SELECT '0' FLAG FROM (SELECT a.tablespace_name FROM (SELECT tablespace_name, SUM(bytes) free FROM dba_free_space GROUP BY tablespace_name) a, (SELECT tablespace_name, SUM(CASE autoextensible WHEN 'YES' THEN maxbytes ELSE bytes END) maxbytes, SUM(bytes) total FROM dba_data_files GROUP BY tablespace_name) b WHERE a.tablespace_name = b.tablespace_name and b.tablespace_name NOT IN ('UNDOTBS1', 'UNDOTBS2') and round((total - free) / b.maxbytes, 4) * 100 <90) UNION ALL SELECT '1' FLAG FROM (SELECT a.tablespace_name FROM (SELECT tablespace_name, SUM(bytes) free FROM dba_free_space GROUP BY tablespace_name) a, (SELECT tablespace_name, SUM(CASE autoextensible WHEN 'YES' THEN maxbytes ELSE bytes END) maxbytes, SUM(bytes) total FROM dba_data_files GROUP BY tablespace_name) b WHERE a.tablespace_name = b.tablespace_name and b.tablespace_name NOT IN ('UNDOTBS1', 'UNDOTBS2') and round((total - free) / b.maxbytes, 4) * 100 >=90) UNION ALL SELECT '2' FLAG FROM (SELECT a.tablespace_name FROM (SELECT tablespace_name, SUM(bytes) free FROM dba_free_space GROUP BY tablespace_name) a, (SELECT tablespace_name, SUM(CASE autoextensible WHEN 'YES' THEN maxbytes ELSE bytes END) maxbytes, SUM(bytes) total FROM dba_data_files GROUP BY tablespace_name) b WHERE a.tablespace_name = b.tablespace_name and b.tablespace_name NOT IN ('UNDOTBS1', 'UNDOTBS2') and round((total - free) / b.maxbytes, 4) * 100 >=95)) UNION ALL SELECT TRIM(DBMS_LOB.SUBSTR(WM_CONCAT(ABC))) DATAVAL FROM (SELECT 'NAME=' || TABLESPACE_NAME || ':SUM=' || SUM_SPACE || ':USED=' || USED_SPACE AS ABC FROM (SELECT D.TABLESPACE_NAME, SPACE SUM_SPACE, BLOCKS SUM_BLOCKS, SPACE - NVL(FREE_SPACE, 0) USED_SPACE FROM (SELECT TABLESPACE_NAME, ROUND(SUM(BYTES) / (1024 * 1024), 2) SPACE, SUM(BLOCKS) BLOCKS FROM DBA_DATA_FILES GROUP BY TABLESPACE_NAME) D, (SELECT TABLESPACE_NAME, ROUND(SUM(BYTES) / (1024 * 1024), 2)FREE_SPACE FROM DBA_FREE_SPACE GROUP BY TABLESPACE_NAME) F WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME(+)) A));
--这条SQL 的物理读主要集中在如下行。
57768 57768 57768 FIXED TABLE FULL X$KTFBUE (cr=10805 pr=4098 pw=0 time=437941 us cost=20 size=6500000 card=100000) 物理读集中在这一行，清空recylce_bin就可以了
--为了减小物理读，处理如下：
select count(*) from dba_recyclebin;
create table dba_recycle_1 as select * from dba_recyclebin;
purge recyclebin;
alter system set recyclebin=off scope=spfile;
purge recyclebin;
purge dba_recyclebin;
alter system set recyclebin=on;
sample:
2w data consume about 14minutes
how to monitor purge speed:
select SOFAR,TOTALWORK,SOFAR,UNITS,TIME_REMAINING from V$SESSION_LONGOPS where SID= and SERIAL#= ;
or
select sum(SPACE) from DBA_RECYCLEBIN;
1.效果如下：
12456 physical reads
变成
0 physical reads
2.sqlhc效果如下：
修改后的等待事件集中于 control file sequential read ，也就是 基表读取 基于内存读取，因此判断有效的减小物理读。
| 1 | 419194613 | WAITING | System I/O | control file sequential read | 1504 |
| 2 | 419194613 | ON CPU | 51 |
修改之前的等待集中于：db file sequential read ， 也就是物理读，基于硬盘读。
| 2 | 4065600310 | WAITING | User I/O | db file sequential read | 14268 |
| 13 | 4065600310 | WAITING | Other | enq: TX - contention | 10226 |
| 14 | 4065600310 | WAITING | User I/O | read by other session | 4447 |
| 15 | 4065600310 | ON CPU | 2305 | ||
| 16 | 4065600310 | WAITING | System I/O | control file sequential read | 482 |
| 17 | 4065600310 | WAITING | Configuration | free buffer waits | 375 |
| 18 | 4065600310 | WAITING | Concurrency | buffer busy waits | 26 |
| 19 | 4065600310 | WAITING | Concurrency | latch: cache buffers chains | 14 |
| 20 | 4065600310 | WAITING | User I/O | Disk file operations I/O | 4 |
| 21 | 4065600310 | WAITING | Other | latch free | 1 |
###############
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: SYS
Number of plan statistics captured: 1
Rows (1st) Rows (avg) Rows (max) Row Source Operation
---------- ---------- ---------- ---------------------------------------------------
1 1 1 SORT AGGREGATE (cr=45126 pr=16392 pw=0 time=1398821 us)
2 2 2 VIEW (cr=45126 pr=16392 pw=0 time=1398447 us cost=190 size=4004 card=2)
2 2 2 UNION-ALL (cr=45126 pr=16392 pw=0 time=1398441 us)
1 1 1 SORT AGGREGATE (cr=33847 pr=12294 pw=0 time=1081992 us)
5 5 5 VIEW (cr=33847 pr=12294 pw=0 time=446432 us cost=142 size=9 card=3)
5 5 5 UNION-ALL (cr=33847 pr=12294 pw=0 time=446432 us)
5 5 5 HASH JOIN (cr=11293 pr=4098 pw=0 time=446424 us cost=47 size=73 card=1)
5 5 5 VIEW (cr=64 pr=0 pw=0 time=6266 us cost=5 size=86 card=2)
5 5 5 HASH GROUP BY (cr=64 pr=0 pw=0 time=6260 us cost=5 size=74 card=2)
12 12 12 VIEW DBA_DATA_FILES (cr=64 pr=0 pw=0 time=4470 us cost=4 size=74 card=2)
12 12 12 UNION-ALL (cr=64 pr=0 pw=0 time=4468 us)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=1082 us cost=2 size=366 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=1080 us cost=1 size=351 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=1079 us cost=1 size=338 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=951 us cost=0 size=310 card=1)
0 0 0 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=142 us cost=1 size=28 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=77 us cost=0 size=0 card=1)(object id 43)
0 0 0 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=0 us cost=0 size=104 card=8)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=1 size=15 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
12 12 12 NESTED LOOPS (cr=47 pr=0 pw=0 time=3348 us cost=2 size=425 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=2373 us cost=1 size=410 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=1494 us cost=1 size=397 card=1)
13 13 13 NESTED LOOPS (cr=13 pr=0 pw=0 time=1353 us cost=0 size=388 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=85 us cost=0 size=310 card=1)
13 13 13 FIXED TABLE FIXED INDEX X$KTFBHC (ind:1) (cr=13 pr=0 pw=0 time=751 us cost=0 size=78 card=1)
13 13 13 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=97 us cost=1 size=9 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=43 us cost=0 size=0 card=1)(object id 43)
13 13 13 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=832 us cost=0 size=104 card=8)
12 12 12 TABLE ACCESS CLUSTER TS$ (cr=17 pr=0 pw=0 time=405 us cost=1 size=15 card=1)
13 13 13 INDEX UNIQUE SCAN I_TS# (cr=4 pr=0 pw=0 time=60 us cost=0 size=0 card=1)(object id 7)
5 5 5 VIEW (cr=11229 pr=4098 pw=0 time=437851 us cost=42 size=180 card=6)
5 5 5 HASH GROUP BY (cr=11229 pr=4098 pw=0 time=437849 us cost=42 size=126 card=6)
330 330 330 VIEW DBA_FREE_SPACE (cr=11229 pr=4098 pw=0 time=29031 us cost=41 size=45066 card=2146)
330 330 330 UNION-ALL (cr=11229 pr=4098 pw=0 time=28921 us)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=224 us cost=3 size=64 card=1)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=223 us cost=3 size=58 card=1)
0 0 0 TABLE ACCESS FULL FET$ (cr=14 pr=0 pw=0 time=221 us cost=3 size=39 card=1)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
0 0 0 INDEX UNIQUE SCAN I_FILE2 (cr=0 pr=0 pw=0 time=0 us cost=0 size=6 card=1)(object id 44)
275 275 275 NESTED LOOPS (cr=18 pr=0 pw=0 time=23671 us cost=5 size=4620 card=66)
275 275 275 NESTED LOOPS (cr=14 pr=0 pw=0 time=22803 us cost=5 size=4224 card=66)
5 5 5 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=57 us cost=5 size=125 card=5)
275 275 275 FIXED TABLE FIXED INDEX X$KTFBFE (ind:1) (cr=0 pr=0 pw=0 time=40889 us cost=0 size=507 card=13)
275 275 275 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=251 us cost=0 size=6 card=1)(object id 44)
55 55 55 NESTED LOOPS (cr=10826 pr=4098 pw=0 time=227265 us cost=27 size=220268 card=2078)
55 55 55 HASH JOIN (cr=10822 pr=4098 pw=0 time=226762 us cost=26 size=2366100 card=23661)
60 60 60 NESTED LOOPS (cr=17 pr=0 pw=0 time=508 us cost=6 size=1855 card=53)
60 60 60 NESTED LOOPS (cr=16 pr=0 pw=0 time=302 us cost=6 size=1855 card=150)
5 5 5 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=49 us cost=5 size=125 card=5)
60 60 60 INDEX RANGE SCAN RECYCLEBIN$_TS (cr=2 pr=0 pw=0 time=158 us cost=0 size=0 card=30)(object id 144)
60 60 60 TABLE ACCESS BY INDEX ROWID RECYCLEBIN$ (cr=1 pr=0 pw=0 time=68 us cost=1 size=100 card=10)
57768 57768 57768 FIXED TABLE FULL X$KTFBUE (cr=10805 pr=4098 pw=0 time=437941 us cost=20 size=6500000 card=100000)
55 55 55 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=194 us cost=0 size=6 card=1)(object id 44)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1420 us cost=6 size=87 card=1)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1417 us cost=6 size=68 card=1)
780 780 780 MERGE JOIN CARTESIAN (cr=3 pr=0 pw=0 time=339 us cost=6 size=12480 card=780)
13 13 13 INDEX FULL SCAN I_FILE2 (cr=1 pr=0 pw=0 time=28 us cost=1 size=78 card=13)(object id 44)
780 780 780 BUFFER SORT (cr=2 pr=0 pw=0 time=113 us cost=5 size=600 card=60)
60 60 60 TABLE ACCESS FULL RECYCLEBIN$ (cr=2 pr=0 pw=0 time=78 us cost=0 size=600 card=60)
0 0 0 TABLE ACCESS CLUSTER UET$ (cr=368 pr=0 pw=0 time=1026 us cost=0 size=52 card=1)
55 55 55 INDEX UNIQUE SCAN I_FILE#_BLOCK# (cr=313 pr=0 pw=0 time=658 us cost=0 size=0 card=1)(object id 9)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
0 0 0 HASH JOIN (cr=11277 pr=4098 pw=0 time=320542 us cost=47 size=73 card=1)
5 5 5 VIEW (cr=64 pr=0 pw=0 time=1324 us cost=5 size=86 card=2)
5 5 5 HASH GROUP BY (cr=64 pr=0 pw=0 time=1323 us cost=5 size=74 card=2)
12 12 12 VIEW DBA_DATA_FILES (cr=64 pr=0 pw=0 time=1140 us cost=4 size=74 card=2)
12 12 12 UNION-ALL (cr=64 pr=0 pw=0 time=1128 us)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=161 us cost=2 size=366 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=160 us cost=1 size=351 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=160 us cost=1 size=338 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=106 us cost=0 size=310 card=1)
0 0 0 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=44 us cost=1 size=28 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=20 us cost=0 size=0 card=1)(object id 43)
0 0 0 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=0 us cost=0 size=104 card=8)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=1 size=15 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
12 12 12 NESTED LOOPS (cr=47 pr=0 pw=0 time=936 us cost=2 size=425 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=852 us cost=1 size=410 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=311 us cost=1 size=397 card=1)
13 13 13 NESTED LOOPS (cr=13 pr=0 pw=0 time=220 us cost=0 size=388 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=72 us cost=0 size=310 card=1)
13 13 13 FIXED TABLE FIXED INDEX X$KTFBHC (ind:1) (cr=13 pr=0 pw=0 time=116 us cost=0 size=78 card=1)
13 13 13 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=71 us cost=1 size=9 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=29 us cost=0 size=0 card=1)(object id 43)
13 13 13 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=507 us cost=0 size=104 card=8)
12 12 12 TABLE ACCESS CLUSTER TS$ (cr=17 pr=0 pw=0 time=99 us cost=1 size=15 card=1)
13 13 13 INDEX UNIQUE SCAN I_TS# (cr=4 pr=0 pw=0 time=34 us cost=0 size=0 card=1)(object id 7)
5 5 5 VIEW (cr=11213 pr=4098 pw=0 time=318873 us cost=42 size=180 card=6)
5 5 5 HASH GROUP BY (cr=11213 pr=4098 pw=0 time=318872 us cost=42 size=126 card=6)
330 330 330 VIEW DBA_FREE_SPACE (cr=11213 pr=4098 pw=0 time=23472 us cost=41 size=45066 card=2146)
330 330 330 UNION-ALL (cr=11213 pr=4098 pw=0 time=23362 us)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=32 us cost=3 size=64 card=1)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=32 us cost=3 size=58 card=1)
0 0 0 TABLE ACCESS FULL FET$ (cr=14 pr=0 pw=0 time=31 us cost=3 size=39 card=1)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
0 0 0 INDEX UNIQUE SCAN I_FILE2 (cr=0 pr=0 pw=0 time=0 us cost=0 size=6 card=1)(object id 44)
275 275 275 NESTED LOOPS (cr=18 pr=0 pw=0 time=19346 us cost=5 size=4620 card=66)
275 275 275 NESTED LOOPS (cr=14 pr=0 pw=0 time=18427 us cost=5 size=4224 card=66)
5 5 5 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=33 us cost=5 size=125 card=5)
275 275 275 FIXED TABLE FIXED INDEX X$KTFBFE (ind:1) (cr=0 pr=0 pw=0 time=31365 us cost=0 size=507 card=13)
275 275 275 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=193 us cost=0 size=6 card=1)(object id 44)
55 55 55 NESTED LOOPS (cr=10810 pr=4098 pw=0 time=146381 us cost=27 size=220268 card=2078)
55 55 55 HASH JOIN (cr=10806 pr=4098 pw=0 time=145987 us cost=26 size=2366100 card=23661)
60 60 60 NESTED LOOPS (cr=17 pr=0 pw=0 time=279 us cost=6 size=1855 card=53)
60 60 60 NESTED LOOPS (cr=16 pr=0 pw=0 time=98 us cost=6 size=1855 card=150)
5 5 5 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=36 us cost=5 size=125 card=5)
60 60 60 INDEX RANGE SCAN RECYCLEBIN$_TS (cr=2 pr=0 pw=0 time=75 us cost=0 size=0 card=30)(object id 144)
60 60 60 TABLE ACCESS BY INDEX ROWID RECYCLEBIN$ (cr=1 pr=0 pw=0 time=48 us cost=1 size=100 card=10)
57768 57768 57768 FIXED TABLE FULL X$KTFBUE (cr=10789 pr=4098 pw=0 time=314543 us cost=20 size=6500000 card=100000)
55 55 55 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=181 us cost=0 size=6 card=1)(object id 44)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1304 us cost=6 size=87 card=1)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1303 us cost=6 size=68 card=1)
780 780 780 MERGE JOIN CARTESIAN (cr=3 pr=0 pw=0 time=397 us cost=6 size=12480 card=780)
13 13 13 INDEX FULL SCAN I_FILE2 (cr=1 pr=0 pw=0 time=17 us cost=1 size=78 card=13)(object id 44)
780 780 780 BUFFER SORT (cr=2 pr=0 pw=0 time=214 us cost=5 size=600 card=60)
60 60 60 TABLE ACCESS FULL RECYCLEBIN$ (cr=2 pr=0 pw=0 time=16 us cost=0 size=600 card=60)
0 0 0 TABLE ACCESS CLUSTER UET$ (cr=368 pr=0 pw=0 time=966 us cost=0 size=52 card=1)
55 55 55 INDEX UNIQUE SCAN I_FILE#_BLOCK# (cr=313 pr=0 pw=0 time=613 us cost=0 size=0 card=1)(object id 9)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
0 0 0 HASH JOIN (cr=11277 pr=4098 pw=0 time=314947 us cost=47 size=73 card=1)
5 5 5 VIEW (cr=64 pr=0 pw=0 time=1281 us cost=5 size=86 card=2)
5 5 5 HASH GROUP BY (cr=64 pr=0 pw=0 time=1279 us cost=5 size=74 card=2)
12 12 12 VIEW DBA_DATA_FILES (cr=64 pr=0 pw=0 time=1090 us cost=4 size=74 card=2)
12 12 12 UNION-ALL (cr=64 pr=0 pw=0 time=1077 us)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=135 us cost=2 size=366 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=135 us cost=1 size=351 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=134 us cost=1 size=338 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=96 us cost=0 size=310 card=1)
0 0 0 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=43 us cost=1 size=28 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=23 us cost=0 size=0 card=1)(object id 43)
0 0 0 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=0 us cost=0 size=104 card=8)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=1 size=15 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
12 12 12 NESTED LOOPS (cr=47 pr=0 pw=0 time=922 us cost=2 size=425 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=840 us cost=1 size=410 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=321 us cost=1 size=397 card=1)
13 13 13 NESTED LOOPS (cr=13 pr=0 pw=0 time=207 us cost=0 size=388 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=70 us cost=0 size=310 card=1)
13 13 13 FIXED TABLE FIXED INDEX X$KTFBHC (ind:1) (cr=13 pr=0 pw=0 time=115 us cost=0 size=78 card=1)
13 13 13 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=75 us cost=1 size=9 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=31 us cost=0 size=0 card=1)(object id 43)
13 13 13 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=508 us cost=0 size=104 card=8)
12 12 12 TABLE ACCESS CLUSTER TS$ (cr=17 pr=0 pw=0 time=98 us cost=1 size=15 card=1)
13 13 13 INDEX UNIQUE SCAN I_TS# (cr=4 pr=0 pw=0 time=32 us cost=0 size=0 card=1)(object id 7)
5 5 5 VIEW (cr=11213 pr=4098 pw=0 time=313442 us cost=42 size=180 card=6)
5 5 5 HASH GROUP BY (cr=11213 pr=4098 pw=0 time=313441 us cost=42 size=126 card=6)
330 330 330 VIEW DBA_FREE_SPACE (cr=11213 pr=4098 pw=0 time=21495 us cost=41 size=45066 card=2146)
330 330 330 UNION-ALL (cr=11213 pr=4098 pw=0 time=21384 us)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=31 us cost=3 size=64 card=1)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=30 us cost=3 size=58 card=1)
0 0 0 TABLE ACCESS FULL FET$ (cr=14 pr=0 pw=0 time=28 us cost=3 size=39 card=1)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
0 0 0 INDEX UNIQUE SCAN I_FILE2 (cr=0 pr=0 pw=0 time=0 us cost=0 size=6 card=1)(object id 44)
275 275 275 NESTED LOOPS (cr=18 pr=0 pw=0 time=17519 us cost=5 size=4620 card=66)
275 275 275 NESTED LOOPS (cr=14 pr=0 pw=0 time=16965 us cost=5 size=4224 card=66)
5 5 5 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=33 us cost=5 size=125 card=5)
275 275 275 FIXED TABLE FIXED INDEX X$KTFBFE (ind:1) (cr=0 pr=0 pw=0 time=29792 us cost=0 size=507 card=13)
275 275 275 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=195 us cost=0 size=6 card=1)(object id 44)
55 55 55 NESTED LOOPS (cr=10810 pr=4098 pw=0 time=145724 us cost=27 size=220268 card=2078)
55 55 55 HASH JOIN (cr=10806 pr=4098 pw=0 time=145276 us cost=26 size=2366100 card=23661)
60 60 60 NESTED LOOPS (cr=17 pr=0 pw=0 time=226 us cost=6 size=1855 card=53)
60 60 60 NESTED LOOPS (cr=16 pr=0 pw=0 time=105 us cost=6 size=1855 card=150)
5 5 5 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=48 us cost=5 size=125 card=5)
60 60 60 INDEX RANGE SCAN RECYCLEBIN$_TS (cr=2 pr=0 pw=0 time=49 us cost=0 size=0 card=30)(object id 144)
60 60 60 TABLE ACCESS BY INDEX ROWID RECYCLEBIN$ (cr=1 pr=0 pw=0 time=16 us cost=1 size=100 card=10)
57768 57768 57768 FIXED TABLE FULL X$KTFBUE (cr=10789 pr=4098 pw=0 time=309625 us cost=20 size=6500000 card=100000)
55 55 55 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=181 us cost=0 size=6 card=1)(object id 44)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1284 us cost=6 size=87 card=1)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1281 us cost=6 size=68 card=1)
780 780 780 MERGE JOIN CARTESIAN (cr=3 pr=0 pw=0 time=176 us cost=6 size=12480 card=780)
13 13 13 INDEX FULL SCAN I_FILE2 (cr=1 pr=0 pw=0 time=28 us cost=1 size=78 card=13)(object id 44)
780 780 780 BUFFER SORT (cr=2 pr=0 pw=0 time=131 us cost=5 size=600 card=60)
60 60 60 TABLE ACCESS FULL RECYCLEBIN$ (cr=2 pr=0 pw=0 time=14 us cost=0 size=600 card=60)
0 0 0 TABLE ACCESS CLUSTER UET$ (cr=368 pr=0 pw=0 time=944 us cost=0 size=52 card=1)
55 55 55 INDEX UNIQUE SCAN I_FILE#_BLOCK# (cr=313 pr=0 pw=0 time=595 us cost=0 size=0 card=1)(object id 9)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
1 1 1 SORT AGGREGATE (cr=11278 pr=4098 pw=0 time=316182 us)
6 6 6 HASH JOIN OUTER (cr=11278 pr=4098 pw=0 time=314554 us cost=47 size=120 card=2)
6 6 6 VIEW (cr=64 pr=0 pw=0 time=1308 us cost=5 size=60 card=2)
6 6 6 HASH GROUP BY (cr=64 pr=0 pw=0 time=1301 us cost=5 size=68 card=2)
13 13 13 VIEW DBA_DATA_FILES (cr=64 pr=0 pw=0 time=1164 us cost=4 size=68 card=2)
13 13 13 UNION-ALL (cr=64 pr=0 pw=0 time=1163 us)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=134 us cost=2 size=356 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=133 us cost=1 size=341 card=1)
0 0 0 NESTED LOOPS (cr=17 pr=0 pw=0 time=131 us cost=1 size=328 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=82 us cost=0 size=310 card=1)
0 0 0 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=45 us cost=1 size=18 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=23 us cost=0 size=0 card=1)(object id 43)
0 0 0 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=0 us cost=0 size=104 card=8)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=1 size=15 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
13 13 13 NESTED LOOPS (cr=47 pr=0 pw=0 time=997 us cost=2 size=399 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=841 us cost=1 size=384 card=1)
13 13 13 NESTED LOOPS (cr=30 pr=0 pw=0 time=311 us cost=1 size=371 card=1)
13 13 13 NESTED LOOPS (cr=13 pr=0 pw=0 time=206 us cost=0 size=362 card=1)
13 13 13 FIXED TABLE FULL X$KCCFN (cr=0 pr=0 pw=0 time=57 us cost=0 size=310 card=1)
13 13 13 FIXED TABLE FIXED INDEX X$KTFBHC (ind:1) (cr=13 pr=0 pw=0 time=114 us cost=0 size=52 card=1)
13 13 13 TABLE ACCESS BY INDEX ROWID FILE$ (cr=17 pr=0 pw=0 time=79 us cost=1 size=9 card=1)
13 13 13 INDEX UNIQUE SCAN I_FILE1 (cr=4 pr=0 pw=0 time=32 us cost=0 size=0 card=1)(object id 43)
13 13 13 FIXED TABLE FIXED INDEX X$KCCFE (ind:1) (cr=0 pr=0 pw=0 time=513 us cost=0 size=104 card=8)
13 13 13 TABLE ACCESS CLUSTER TS$ (cr=17 pr=0 pw=0 time=96 us cost=1 size=15 card=1)
13 13 13 INDEX UNIQUE SCAN I_TS# (cr=4 pr=0 pw=0 time=37 us cost=0 size=0 card=1)(object id 7)
6 6 6 VIEW (cr=11214 pr=4098 pw=0 time=313061 us cost=42 size=180 card=6)
6 6 6 HASH GROUP BY (cr=11214 pr=4098 pw=0 time=313051 us cost=42 size=126 card=6)
361 361 361 VIEW DBA_FREE_SPACE (cr=11214 pr=4098 pw=0 time=5630 us cost=41 size=45066 card=2146)
361 361 361 UNION-ALL (cr=11214 pr=4098 pw=0 time=5629 us)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=31 us cost=3 size=64 card=1)
0 0 0 NESTED LOOPS (cr=14 pr=0 pw=0 time=30 us cost=3 size=58 card=1)
0 0 0 TABLE ACCESS FULL FET$ (cr=14 pr=0 pw=0 time=29 us cost=3 size=39 card=1)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
0 0 0 INDEX UNIQUE SCAN I_FILE2 (cr=0 pr=0 pw=0 time=0 us cost=0 size=6 card=1)(object id 44)
306 306 306 NESTED LOOPS (cr=18 pr=0 pw=0 time=4650 us cost=5 size=4620 card=66)
306 306 306 NESTED LOOPS (cr=14 pr=0 pw=0 time=3830 us cost=5 size=4224 card=66)
6 6 6 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=47 us cost=5 size=125 card=5)
306 306 306 FIXED TABLE FIXED INDEX X$KTFBFE (ind:1) (cr=0 pr=0 pw=0 time=22825 us cost=0 size=507 card=13)
306 306 306 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=199 us cost=0 size=6 card=1)(object id 44)
55 55 55 NESTED LOOPS (cr=10811 pr=4098 pw=0 time=143961 us cost=27 size=220268 card=2078)
55 55 55 HASH JOIN (cr=10807 pr=4098 pw=0 time=143513 us cost=26 size=2366100 card=23661)
60 60 60 NESTED LOOPS (cr=18 pr=0 pw=0 time=279 us cost=6 size=1855 card=53)
60 60 60 NESTED LOOPS (cr=17 pr=0 pw=0 time=157 us cost=6 size=1855 card=150)
6 6 6 TABLE ACCESS FULL TS$ (cr=14 pr=0 pw=0 time=44 us cost=5 size=125 card=5)
60 60 60 INDEX RANGE SCAN RECYCLEBIN$_TS (cr=3 pr=0 pw=0 time=20 us cost=0 size=0 card=30)(object id 144)
60 60 60 TABLE ACCESS BY INDEX ROWID RECYCLEBIN$ (cr=1 pr=0 pw=0 time=29 us cost=1 size=100 card=10)
57768 57768 57768 FIXED TABLE FULL X$KTFBUE (cr=10789 pr=4098 pw=0 time=314286 us cost=20 size=6500000 card=100000)
55 55 55 INDEX UNIQUE SCAN I_FILE2 (cr=4 pr=0 pw=0 time=187 us cost=0 size=6 card=1)(object id 44)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1273 us cost=6 size=87 card=1)
0 0 0 NESTED LOOPS (cr=371 pr=0 pw=0 time=1271 us cost=6 size=68 card=1)
780 780 780 MERGE JOIN CARTESIAN (cr=3 pr=0 pw=0 time=400 us cost=6 size=12480 card=780)
13 13 13 INDEX FULL SCAN I_FILE2 (cr=1 pr=0 pw=0 time=17 us cost=1 size=78 card=13)(object id 44)
780 780 780 BUFFER SORT (cr=2 pr=0 pw=0 time=251 us cost=5 size=600 card=60)
60 60 60 TABLE ACCESS FULL RECYCLEBIN$ (cr=2 pr=0 pw=0 time=15 us cost=0 size=600 card=60)
0 0 0 TABLE ACCESS CLUSTER UET$ (cr=368 pr=0 pw=0 time=925 us cost=0 size=52 card=1)
55 55 55 INDEX UNIQUE SCAN I_FILE#_BLOCK# (cr=313 pr=0 pw=0 time=591 us cost=0 size=0 card=1)(object id 9)
0 0 0 TABLE ACCESS CLUSTER TS$ (cr=0 pr=0 pw=0 time=0 us cost=0 size=19 card=1)
0 0 0 INDEX UNIQUE SCAN I_TS# (cr=0 pr=0 pw=0 time=0 us cost=0 size=0 card=1)(object id 7)
********************************************************************************
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdc 0.00 0.00 14.00 2.00 0.11 0.02 16.06 0.01 0.38 0.38 0.60
sdc3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdd 0.00 0.00 499.00 0.00 3.90 0.00 16.00 0.20 0.41 0.41 20.40
sdd3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sde 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sde3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdf 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdf3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdh 0.00 0.00 16.00 0.00 0.12 0.00 16.00 0.00 0.12 0.12 0.20
sdh3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdi 0.00 0.00 497.00 3.00 3.88 0.02 15.97 0.14 0.29 0.29 14.40
sdi3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdj 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdj3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdk 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdk3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
emcpowerb 0.00 0.00 30.00 2.00 0.23 0.02 16.03 0.01 0.28 0.28 0.90
emcpowerb3 0.00 0.00 30.00 2.00 0.23 0.02 16.03 0.01 0.28 0.28 0.90
emcpowera 0.00 0.00 995.00 3.00 7.77 0.02 15.99 0.36 0.36 0.36 35.60
emcpowera3 0.00 0.00 995.00 3.00 7.77 0.02 15.99 0.36 0.36 0.36 35.60
emcpowerc 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
emcpowerc3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
emcpowerd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
emcpowerd3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
VxVM21000 0.00 0.00 0.00 1.00 0.00 0.00 2.00 0.00 0.00 0.00 0.00
VxVM21001 0.00 0.00 0.00 2.00 0.00 0.02 16.50 0.00 0.50 0.50 0.10
VxVM21002 0.00 0.00 1024.00 2.00 8.00 0.02 16.00 0.37 0.36 0.36 37.20
VM21002 0.00 0.00 2018.81 0.00 15.77 0.00 16.00 0.76 0.38 0.38 76.44 <- running time
Statistics
----------------------------------------------------------
18571 recursive calls
501 db block gets
48231 consistent gets
12456 physical reads
0 redo size
725 bytes sent via SQL*Net to client
524 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
4 sorts (memory)
0 sorts (disk)
1 rows processed
0.4ms /per io
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 2 0.19 0.21 0 420 0 0
Execute 2 0.00 0.00 0 0 0 0
Fetch 4 10.40 24.74 57116 82448 3076 2
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 8 10.60 24.96 57116 82868 3076 2
############### uat
0.07ms/per io
SQL ID: 3mhmz5nbhgn2q Plan Hash: 158949995
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.12 0.12 0 228 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 1.24 1.25 16392 25049 509 1
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 4 1.37 1.38 16392 25277 509 1
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util
sda 49.50 7.92 190.10 3.96 23.25 0.05 245.88 0.59 3.08 1.62 31.49
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 19.80 7.92 3.96 3.96 0.09 0.05 36.00 0.16 19.62 17.50 13.86
sda3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 <- running time
Statistics
----------------------------------------------------------
17288 recursive calls
491 db block gets
45111 consistent gets
16396 physical reads
0 redo size
724 bytes sent via SQL*Net to client
524 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
4 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> spool off
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解题关键:了解转移方程即可. 转移方程:$dp[l][r] = dp[l + 1][r - 1] + 2$ 若该区间左右端点成功匹配.然后对区间内的子区间取max即可. nyoj15:求需要添加的最少 ...