ORACLE parent latch和children latch
About parent vs child latches. There is no fundamental low level difference between parent and child latches, they are all small regions of memory modified with atomic test-and-set style opcodes.
You see parent (and solitary) latches from x$ksllt where kslltcnm = 0 and child latches have Kslltcnm > 0 (their child number is stored there).
V$LATCH_PARENT shows all latches with kslltcnm 0, V$LATCH_CHILDREN shows all latches with cnm > 0. V$LATCH just summarizes & groups all statistics up using the latch number, it doesn't care about parent vs child latches.
It's up to Oracle, how it uses the child and parent latches, normally when child latches are used, parent latches don't get used much (or at all), since all resources to be protected have been spread between child latches already.
今天看到书中讲LATCH的时候提到了两个视图V$LATCH_CHILDREN和V$LATCH_PARENT ，不太清楚两者的区别，去百度了一下，还没百度到，GOOGLE了才找到一篇相关的文章。
看了上面的讲解，我个人理解就是二者其实没什么区别，完全取决于ORACLE如何使用。
相关文档：
Oracle数据导入导出imp/exp命令
Oracle 数据导入导出imp/exp就相当于oracle数据还原与备份。exp命令可以把数据从远程数据库服务器导出到本地的dmp文件，imp命令可以把 dmp文件从本地导入到远处的数据库服务器中。 利用这个功能可以构建两个相同的数据库，一个用来测试，一个用来正式使用。
执行� ......
SQL> SQLPLUS / AS SYSDBA
SQL> exec dbms_workload_repository.create_snapshot
SQL> exec:snap_id:=dbms_workload_repository.create_snapshot
SQL> var snap_id number
SQL> print snap_id
SQL> @?/rdbms/admin/awrrpt.sql
OracleAWR速查
1.查看当前的AWR保存策略
select * fro ......
登陆ORACLE时出现：ORA-12637 包接受失败 错误
解决方法：在\oracle\product\10.2.0\client_1\NETWORK\ADMIN 中找到sqlnet.ora文件，
把修改 SQLNET.AUTHENTICATION_SERVICES= (NONE)就可以了。 ......
alter system set nls_length_semantics='BYTE' scope=both
sql>show parameter length
NAME TYPE
------------------------------------ --------------------- ......
