1.truncate和delete删除表中的数据；drop是将表从数据字典中删除，并清空表中的数据。 2.truncate和drop 为DDL语句，不会产生重做日志；delete为DML语句，会产生重做日志。 3.truncate之后会降低高水位线，而delete ...

Reference NotesThe formula for the cost (using the CPU Costing Model) of a query is: Cost = ( #SRds * sreadtime + #MRds * mreadtime + #CPUCycles / cpuspeed ) / sreadtime where: #SRds = number of sin ...

Goal To trace the CBO working out the execution path (event 10053) Facts Solution To start the CBO trace enter the following command: ALTER SESSION SET EVENTS='10053 trace name context forever, le ...

Solution The following script will find SQL with many disk reads: -- ------------------------ -- Find SQL Statements that -- require a lot of disk -- reads. -- ------------------------ SELECT * FROM ...

Use these statements to determine the physical Disk I/O performed on Tablespaces or Data Files. Tablespace Files Physical Reads and Writes set pages 500 lines 110 clear col bre buffer col tablespac ...

If you would to determine the amount of memory database processes are consuming consider the following script set lines 110 col unm format a30 hea "USERNAME (SID,SERIAL#)" col pus format 999,990.9 h ...

set pages500 lines110 trims on clear col col name format a30 col username format a20 break on username nodup skip 1 select vses.username||':'||vsst.sid||','||vses.serial# username, vstt.name, max(vs ...

Overview Most Oracle databases use locally managed tablespaces (LMT) today - dictionary managed tablespaces (DMT) are now obsolet. The reasons to use LMTs are the following: Object fragmentation you ...