Oracle DBA学习篇之SQL_TRACE

SQL_TRACE

set linesize 10000;
set pagesize 20000;
set serveroutput on;
alter session set sql_trace=true;
select count(*) from firefox;
alter session set sql_trace=false;

--查看sql_trace trace file
select * from v$diag_info where name like 'Default%';
select sid,serial# from v$session ;

variable x number;
exec :x:=1;
alter session set events '10046 trace name context forever,level 12';
select count(*) from firefox where object_id=:x;
alter session set events '10046 trace name context off';
select object_name from dba_objects where object_id=426 or object_id=427

SQL> select * from aux_stats$;
收集系统信息
exec dbms_stats.gather_system_stats(gathering_mode=>'start');
alter system flush_cache;
select count(*) from fire_t01;
select * from aux_stats$;

初始化参数;
db_file_multiblock_read_count
查看数据表一共有多少个块;
select blocks from user_tables where table_name='FIREFOX';

set autotrace on;
SELECT * FROM FIREFOX;

SELECT /*+ blocks/k=cost */ 1029/10.4 from dual;

查看数据块大小
show parameter db_block_size;

select * from sys.aux_stats$;
SYSSTATS_MAIN    IOSEEKTIM    10
SYSSTATS_MAIN    IOTFRSPEED    4096
SYSSTATS_MAIN    CPUSPEEDNW    2657.0122

#单块读的时间
sreadtim = IOSEEKTIM+(size of one block/IOTFRSPEED).
=10+(8192/4096)=12
#多块数据块读取的时间
mreadtim=IOSEEKTIM+(MBRC * SIZE OF one block) / IOTFRSPEED)
=10+((16*8192)/4096)=42
io_cost=(1046(blocks)/16)*(42/12)=232.75
cpu_cost=cpu_cost=cpucycles/(cpuspeed*sreadtim)
=116192792/(2657.0122*12*1000)=4.48
cost=io_cost+cpu_cost = 232.75 + 4.48 =
如何查看cpucycles:PLAN_TABLE、PLAN_TABLE$;

create table firefox1 as select * from firefox where rownum<100;
create index idx_firefox on firefox(object_id);
create index idx_firefox1 on firefox1(object_id);

begin
dbms_stats.gather_table_stats(
user,
'firefox',
cascade => true,
estimate_percent => null,
method_opt =>'for all columns size 1'
);
end;
/

begin
dbms_stats.gather_table_stats(
user,
'firefox1',
cascade => true,
estimate_percent => null, --完全精确地分析;
method_opt =>'for all columns size 1'
);
end;
/

alter session set events '10053 trace name context forever,level 12';
select * from firefox,firefox1 where firefox.object_id = firefox1.object_id;
alter session set events '10053 trace name context off';
select * from v$diag_info where name like 'Default%';

对SGA区的动态调整;
SQL> show sga;

网络连接 --session &processes;
SQL> select username,paddr from v$session where username is not null;

USERNAME    PADDR
------------------------------ ----------------
SYS    00000000F04DAE60
SYS    00000000F04DAE60
C##SCOTT    00000000F04DBEA0

select addr from v$process where background is null and addr='00000000F04DAE60';
select * from v$process where background is null and addr='00000000F04DAE60';

set autotrace on stat;
select username,paddr from v$session where username is not null;
select addr from v$process where background is null and addr='00000000F04DAE60';

CBO计算成本时索引的权重修正值.
show parameter OPTIMIZER_INDEX_COST_ADJ;
alter session set OPTIMIZER_INDEX_COST_ADJ=10;
优化器--optimizer_mode
first_rows [1|10|100|1000]
first
优化器--optimizer_dynamic_sampling
动态采样的级别0to10
默认值(9i 1, >= 10g 2)

查看当前sql/plus 的SID
SELECT sid, serial# FROM v$session WHERE audsid=SYS_CONTEXT('USERENV','SESSIONID');
select a.name,b.value from v$sesstat b.v$statname a where a.static#=b.statistic# and a.name ='CPU used by this session' and sid=69;

显示各种文件的I/O统计信息
- 数据文件,临时文件,控制文件,日志文件,归档文件...
select file_no,filetype_name,LARGE_READ_MEGABYTES,SMALL_READ_MEGABYTES,SMALL_SYNC_READ_LATENCY from v$iostat_file;
对象--v$segstat
获得某对象的各类统计信息;
select * from v$segstat where obj#=79605 and statistic_name='physical_reads';