解析6-2
解析6-2<BR>sorts (rows) 511,574 606.9 6.8<BR>summed dirty queue length 430 0.5 0.0<BR>switch current to new buffer 59,534 70.6 0.8<BR>table fetch by rowid 2,094,274 2,484.3 27.7<BR>这是通过索引或者where rowid=语句来取得的行数,当然这个值越大越好。<BR>table fetch continued row 408 0.5 0.0<BR>这是发生行迁移的行。当行迁移的情况比较严重时,需要对这部分进行优化。<BR>检查行迁移的方法:<BR>运行$ORACLE_HOME/rdbms/admin/utlchain.sql<BR>analyze table table_name list chained rows into CHAINED_ROWS<BR>select * from CHAINED_ROWS where table_name='table_name';<BR>清除的方法:<BR>方法1:create table table_name_tmp as select * from table_name where rowed in (select head_rowid from chained_rows);<BR> Delete from table_name where rowed in (select head_rowid from chained_rows);<BR> Insert into table_name select * from table_name_tmp;<BR>方法2:create table table_name_tmp select * from table_name ;<BR>truncate table table_name<BR>insert into table_name select * from table_name_tmp<BR>方法3:用exp工具导出表,然后删除这个表,最后用imp工具导入这表<BR>方法4:alter table table_name move tablespace tablespace_name,然后再重新表的索引<BR>上面的4种方法可以用以消除已经存在的行迁移现象,但是行迁移的产生很多情况下时由于PCT_FREE参数设置的太小所导致,所以需要调整PCT_FREE参数的值。<BR>table scan blocks gotten 299,249 355.0 4.0<BR>table scan rows gotten 1,912,851 2,269.1 25.3<BR>table scans (long tables) 0 0.0 0.0<BR>
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