Oracle统计分析

1.oracle11g查看自动收集统计信息是否开启

SQL> select client_name,status from dba_autotask_client;

CLIENT_NAME                                                      Status
---------------------------------------------------------------- --------
auto optimizer stats collection                                  ENABLED

　https://blog.csdn.net/xqzhang8/article/details/72758208

 2.手动分析某张表

exec dbms_stats.gather_table_ststs('ownname','tabname');

DBMS_STATS.GATHER_TABLE_STATS (   ownname          VARCHAR2,     tabname          VARCHAR2,     partname         VARCHAR2,   estimate_percent NUMBER,     block_sample     BOOLEAN,   method_opt       VARCHAR2,   degree           NUMBER,   granularity      VARCHAR2,     cascade          BOOLEAN,   stattab          VARCHAR2,     statid           VARCHAR2,   statown          VARCHAR2,   no_invalidate    BOOLEAN,   force            BOOLEAN);

参数说明:
ownname:要分析表的拥有者
tabname:要分析的表名.
partname:分区的名字,只对分区表或分区索引有用.
estimate_percent:采样行的百分比,取值范围[0.000001,100],null为全部分析,不采样. 常量:DBMS_STATS.AUTO_SAMPLE_SIZE是默认值,由oracle决定最佳取采样值.
block_sapmple:是否用块采样代替行采样.
method_opt:决定histograms信息是怎样被统计的.method_opt的取值如下(默认值为FOR ALL COLUMNS SIZE AUTO):
for all columns:统计所有列的histograms.
for all indexed columns:统计所有indexed列的histograms.
for all hidden columns:统计你看不到列的histograms
for columns <list> SIZE <N> | REPEAT | AUTO | SKEWONLY:统计指定列的histograms.N的取值范围[1,254]; REPEAT上次统计过的histograms;AUTO由oracle决定N的大小;SKEWONLY multiple end-points with the same value which is what we define by "there is skew in thedata
degree:决定并行度.默认值为null.
granularity:Granularity of statistics to collect ,only pertinent if the table is partitioned.
cascade:是收集索引的信息.默认为FALSE.
stattab:指定要存储统计信息的表,statid如果多个表的统计信息存储在同一个stattab中用于进行区分.statown存储统计信息表的拥有者.以上三个参数若不指定,统计信息会直接更新到数据字典.
no_invalidate: Does not invalidate the dependent cursors if set to TRUE. The procedure invalidates the dependent cursors immediately if set to FALSE.
force:即使表锁住了也收集统计信息.
例子:
execute dbms_stats.gather_table_stats(ownname => 'owner',tabname => 'table_name' ,estimate_percent => null ,method_opt => 'for all indexed columns' ,cascade => true)

　3.对象统计信息锁定的解决办法（ORA-20005/ORA-38029）

　　解锁单个对象

　　先查出被锁定的表select table_name from user_tab_statistics where stattype_locked is not null;

　　然后再解锁对象

　　exec dbms_stats.unlock_table_stats(user,'表名');

　　参考资料：http://blog.itpub.net/29867/viewspace-730902/

参考资料：

https://www.cndba.cn/Expect-le/article/1900　

https://www.linuxidc.com/Linux/2011-07/39435p2.htm