ORACLE性能监控SQL语句

    监控当前数据库谁在运行什么SQL语句

　　SELECT osuser, username, sql_text from v$session a, v$sqltext b
　　where a.sql_address =b.address order by address, piece;

　　分析表

　　analyze table tablename compute statistics for all indexes;
　　analyze table tablename compute statistics for all indexed columns;
　　analyze table tablename compute statistics for table;

　　监控事例的等待

　　select event,sum(decode(wait_Time,0,0,1)) "Prev",
　　sum(decode(wait_Time,0,1,0)) "Curr",count(*) "Tot"
　　from v$session_Wait
　　group by event order by 4;

　　查看碎片程度高的表

　　SELECT segment_name table_name , COUNT(*) extents
　　FROM dba_segments WHERE owner NOT IN (SYS, SYSTEM) GROUP           BY segment_name

　　HAVING COUNT(*) = (SELECT MAX( COUNT(*) FROM dba_segments GROUP BY segment_name);

　　表、索引的存储情况检查

　　select segment_name,sum(bytes),count(*) ext_quan from dba_extents where
　　tablespace_name=&tablespace_name and segment_type=TABLE group by tablespace_name,segment_name;

　　select segment_name,count(*) from dba_extents where segment_type=INDEX and owner=&owner

　　group by segment_name;

　　找使用CPU多的用户session

　　12是cpu used by this session

　　select a.sid,spid,status,substr(a.program,1,40)   prog,a.terminal,osuser,value/60/100 value

　　from v$session a,v$process b,v$sesstat c

　　where c.statistic#=12 and c.sid=a.sid and a.paddr=b.addr order by value desc;

　　监控表空间的 I/O 比例

　　select df.tablespace_name name,df.file_name "file",f.phyrds pyr,

　　f.phyblkrd pbr,f.phywrts pyw, f.phyblkwrt pbw

　　from v$filestat f, dba_data_files df

　　where f.file# = df.file_id

　　order by df.tablespace_name;

　　回滚段的争用情况

　　select name, waits, gets, waits/gets "Ratio"

　　from v$rollstat a, v$rollname b

　　where a.usn = b.usn;

　　在某个用户下找所有的索引

　　select user_indexes.table_name, user_indexes.index_name,uniqueness, column_name

　　from user_ind_columns, user_indexes

　　where user_ind_columns.index_name = user_indexes.index_name

　　and user_ind_columns.table_name = user_indexes.table_name

　　order by user_indexes.table_type, user_indexes.table_name,

　　user_indexes.index_name, column_position;

　　监控文件系统的 I/O 比例

　　select substr(a.file#,1,2) "#", substr(a.name,1,30) "Name",

　　a.status, a.bytes, b.phyrds, b.phywrts

　　from v$datafile a, v$filestat b

　　where a.file# = b.file#;

　　监控 SGA 中字典缓冲区的命中率

　　select parameter, gets,Getmisses , getmisses/(gets+getmisses)*100 "miss ratio",

　　(1-(sum(getmisses)/ (sum(gets)+sum(getmisses))))*100 "Hit ratio"

　　from v$rowcache

　　where gets+getmisses <>0

　　group by parameter, gets, getmisses;

　　监控 SGA 中共享缓存区的命中率，应该小于1％

　　select sum(pins) "Total Pins", sum(reloads) "Total Reloads",

　　sum(reloads)/sum(pins) *100 libcache

　　from v$librarycache;



select sum(pinhits-reloads)/sum(pins) "hit radio",sum(reloads)/sum(pins) "reload percent"

　　from v$librarycache;

　　监控 SGA 的命中率

　　select a.value + b.value "logical_reads", c.value "phys_reads",

　　round(100 * ((a.value+b.value)-c.value) / (a.value+b.value)) "BUFFER HIT RATIO"

　　from v$sysstat a, v$sysstat b, v$sysstat c

　　where a.statistic# = 38 and b.statistic# = 39

　　and c.statistic# = 40;

　　监控 SGA 中重做日志缓存区的命中率，应该小于1％

　　SELECT name, gets, misses, immediate_gets, immediate_misses,

　　Decode(gets,0,0,misses/gets*100) ratio1,

　　Decode(immediate_gets+immediate_misses,0,0,

　　immediate_misses/(immediate_gets+immediate_misses)*100) ratio2

　　FROM v$latch WHERE name IN (redo allocation, redo copy);

　　显示所有数据库对象的类别和大小

　　select count(name) num_instances ,type ,sum(source_size) source_size ,

　　sum(parsed_size) parsed_size ,sum(code_size) code_size ,sum(error_size) error_size,

　　sum(source_size) +sum(parsed_size) +sum(code_size) +sum(error_size) size_required

　　from dba_object_size

　　group by type order by 2;

　　监控内存和硬盘的排序比率，最好使它小于 .10，增加 sort_area_size

　　SELECT name, value FROM v$sysstat WHERE name IN (sorts (memory), sorts (disk));

　　监控字典缓冲区

　　SELECT (SUM(PINS - RELOADS)) / SUM(PINS) "LIB CACHE" FROM V$LIBRARYCACHE;

　　SELECT (SUM(GETS - GETMISSES - USAGE - FIXED)) / SUM(GETS) "ROW CACHE" FROM V$ROWCACHE;

　　SELECT SUM(PINS) "EXECUTIONS", SUM(RELOADS) "CACHE MISSES WHILE EXECUTING" FROM V$LIBRARYCACHE;

　　后者除以前者,此比率小于1％,接近0％为好。

　　SELECT SUM(GETS) "DICTIONARY GETS",SUM(GETMISSES) "DICTIONARY CACHE GET MISSES"

　　FROM V$ROWCACHE

　　监控 MTS

　　select busy/(busy+idle) "shared servers busy" from v$dispatcher;

　　此值大于0.5时，参数需加大

　　select sum(wait)/sum(totalq) "dispatcher waits" from v$queue where type=dispatcher;

　　select count(*) from v$dispatcher;

　　select servers_highwater from v$mts;

　　servers_highwater接近mts_max_servers时，参数需加大

　　碎片程度

　　select tablespace_name,count(tablespace_name) from dba_free_space group by tablespace_name

　　having count(tablespace_name)>10;

　　alter tablespace name coalesce;

　　alter table name deallocate unused;

　　create or replace view ts_blocks_v as

　　select tablespace_name,block_id,bytes,blocks,free space segment_name from dba_free_space

　　union all

　　select tablespace_name,block_id,bytes,blocks,segment_name from dba_extents;

　　select * from ts_blocks_v;

　　select tablespace_name,sum(bytes),max(bytes),count(block_id) from dba_free_space

　　group by tablespace_name;



四、SQL语句执行效率问题
　　1．检查占用CPU时间比较长的sql语句:
　　select sql_text,cpu_time from v$sql where cpu_time >1e7 order by cpu_time
　　2．执行效率最差的10条sql语句
　　SELECT * FROM ( SELECT PARSING_USER_ID EXECUTIONS SORTS,
　　 COMMAND_TYPE, DISK_READS, sql_text FROM v$sqlarea
　　 ORDER BY disk_reads DESC) WHERE ROWNUM<10 ;
　　3．利用V_$SQLAREA视图提供了执行的细节。（执行、读取磁盘和读取缓冲区的次数）
　　s select SQL_TEXT,EXECUTIONS,DISK_READS,COMMAND_TYPE,OPTIMIZER_MODE, SHARABLE_MEM,BUFFER_GETS from v$sqlarea
　　•
　　数 数据列
　　EXECUTIONS：执行次数
　　DISK_READS：读盘次数
　　COMMAND_TYPE：命令类型（3:select,2:insert;6:update;7delete;47:pl/sql程序单元）
　　OPTIMIZER_MODE：优化方式
　　SQL_TEXT：Sql语句
　　SHARABLE_MEM：占用shared pool的内存多少
　　BUFFER_GETS：读取缓冲区的次数
　　• 用途
　　1、帮忙找出性能较差的SQL语句
　　2、帮忙找出最高频率的SQL
　　3、帮忙分析是否需要索引或改善联接
　　4. 监控当前Oracle的session，如出现时钟的标志，表示此进程中的sql运行时间较长。