advantages of using HugePages

here are the advantages of using hugepages picked up from oracle online doc

The following are the advantages of using HugePages:

  • Increased performance through increased TLB hits.
  • Pages are locked in memory and are never swapped out which guarantees that shared memory like SGA remains in RAM.
  • Contiguous pages are preallocated and cannot be used for anything else but for System V shared memory (e.g. SGA)
  • Less bookkeeping work for the kernel for that part of virtual memory due to larger page sizes

 

a good file sync project。。recommended

http://code.google.com/p/sersync/

 

Introduce

sersync主要用于服务器同步,web镜像等功能。基于boost1.43.0,inotify api,rsync command.开发。目前使用的比较多的同步解决方案是inotify-tools+rsync ,另外一个是google开源项目Openduckbill(依赖于inotify- tools),这两个都是基于脚本语言编写的。相比较上面两个项目,本项目优点是:

  1. sersync是使用c++编写,而且对linux系统文件系统产生的临时文件和重复的文件操作进行过滤(详细见附录,这个过滤脚本程序没有实现),所以在结合rsync同步的时候,节省了运行时耗和网络资源。因此更快。
  2. 相比较上面两个项目,sersync配置起来很简单,其中bin目录下已经有基本上静态编译的2进制文件,配合bin目录下的xml配置文件直接使用即可。
  3. 另外本项目相比较其他脚本开源项目,使用多线程进行同步,尤其在同步较大文件时,能够保证多个服务器实时保持同步状态。
  4. 本项目有出错处理机制,通过失败队列对出错的文件重新同步,如果仍旧失败,则按设定时长对同步失败的文件重新同步。
  5. 本项目自带crontab功能,只需在xml配置文件中开启,即可按您的要求,隔一段时间整体同步一次。无需再额外配置crontab功能。
  6. 本项目socket与http插件扩展,满足您二次开发的需要。

attention please…exp on oracle 11gr2

the reason why some tables have not bee exported is that some tables contains not data,in oracle 11g,the exp tools will not export the table has no data,you need to use expdp.In oracle 11g, exp ignore the table create script or DDL which contains 0 row data.that’s why here comes some “alter table..” section without “create table..” section in front.

http://www.bangela.org/archives/294

export and import dump file with constraints

if you are trying to import the dump file to db while the tables contain constraints,you may got following error information:

***********************************************************

IMP-00017: following statement failed with ORACLE error 942
“ALTER TABLE “R_MSGSTRUCT_RECIPIENT_DELIVINF” ADD CONSTRAINT “F1R_MSGSTRUCT_”
“RECI” FOREIGN KEY (“FK_MESSAGESTRUCT_ID”) REFERENCES “NC_MESSAGESTRUCT” (“P”
“K_MS_ID”) ENABLE NOVALIDATE”
IMP-00003: ORACLE error 942 encountered
ORA-00942: table or view does not exist
IMP-00017: following statement failed with ORACLE error 942
“ALTER TABLE “R_MSGSTRUCT_RECIPIENT_DELIVINF” ADD CONSTRAINT “F3R_MSGSTRUCT_”
“RECI” FOREIGN KEY (“FK_RECIPIENT_ID”) REFERENCES “NC_RECIPIENT” (“PK_RECIPI”
“ENT_ID”) ENABLE NOVALIDATE”
IMP-00003: ORACLE error 942 encountered
ORA-00942: table or view does not exist

*************************************************************

bad luck,maybe u need to manully resolve those problems.it seems exp has some limitations while handling the constraints