direct path read 研究

SQL> select * from v$mystat where rownum<2;

       SID STATISTIC#	   VALUE
---------- ---------- ----------
      1141	    0	       0

SQL> select count(*) from P800;

  COUNT(*)
----------
   5566720



SESSION_ID	           1141	
SQL_ID	               fzt58wuyrqphq	
MACHINE	               node01	
BLOCKING_SESSION		
SAMPLE_TIME	10-4月 -19 06.19.34.270 下午	
MODULE	               SQL*Plus	
PROGRAM	              sqlplus@node01 (TNS V1-V3)	
EVENT	             direct path read	
P1	                 4	
P1TEXT	         file number	
P2	            88760	
P2TEXT	         first dba	
P3	8	
P3TEXT          	block cnt	
SQL_TEXT	select count(*) from P800	


通过direct path read事件的p1,p2,p3值我们可以定位到该事件在哪个对象上发生等待
P1: File_id for the read call

P2: Start block_id for the read call

P3: Number of blocks in the read call


select owner,segment_name,segment_type,partition_name from dba_extents where file_id=4 and 88760 between block_id and block_id+blocks-1;

SQL>  select owner,segment_name,segment_type,partition_name from dba_extents where file_id=4 and 88760 between block_id and block_id+blocks-1;

OWNER	   SEGMENT_NAME 		  SEGMENT_TYPE			 PARTITION_NAME
---------- ------------------------------ ------------------------------ ------------------------------------------------------------------------------------------
TEST	   P800 			  TABLE