【IT168 服务器学院】1.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(*)
　　from v$session_wait
　　group by event order by 4;

　　2.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;

　　3.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

　　4.监空文件系统的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#

　　5.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;

　　6. 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;

　　7. 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;

　　8. 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;

　　9. 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;

　　10. 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'');

　　11. 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)'');

　　
　　12. 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;

　　13. 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

　　14. 找ORACLE字符集

　　select * from sys.props$ where name=''NLS_CHARACTERSET'';

　　15. 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

　　16. 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;

　　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);

　　17. 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;

　　18、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;

　　20.监控log_buffer的使用情况：(值最好小于1%，否则增加log_buffer 的大小)
　　select rbar.name,rbar.value,re.name,re.value,(rbar.value*100)/re.value||''%'' "radio"
　　from v$sysstat rbar,v$sysstat re
　　where rbar.name=''redo buffer allocation retries''
　　and re.name=''redo entries'';

　　
　　19、查看运行过的SQL语句：

　　SELECT SQL_TEXT
　　FROM V$SQL