[20171117]参数filesystemio_options.txt-白红宇

[20171117]参数filesystemio_options.txt

--//前几天看别人的awr报表发现设置参数filesystemio_options=setall,问为什么?对方给出一个链接,某某人都是这样设置的,

--//自己很无语,我希望对方能提出自己的见解.

--//首先给出oracle官方的解析:

9.1.1.2 FILESYSTEMIO_OPTIONS Initialization Parameter

You can use the FILESYSTEMIO_OPTIONS initialization parameter to enable or disable asynchronous I/O or direct I/O on

file system files. This parameter is platform-specific and has a default value that is best for a particular platform.

FILESYTEMIO_OPTIONS can be set to one of the following values:

ASYNCH: enable asynchronous I/O on file system files, which has no timing requirement for transmission.

DIRECTIO: enable direct I/O on file system files, which bypasses the buffer cache.

SETALL: enable both asynchronous and direct I/O on file system files.

NONE: disable both asynchronous and direct I/O on file system files.

--//我以前在学习时也测试过这个参数,因为对于os没有相关的命令了解某个文件的缓存情况,我仅仅在dg上测试,因为没有负载很难了解

--//该参数的设置的效果,仅仅在生产系统遇到一个存储的问题,获得一个小工具nocache,一下子茅舍顿开.

--//参考链接:

--//首先在讲解之前,我仅仅说明数据库采用文件系统的模式,ASM不在讨论范围.先讲讲我以前遇到的问题.

1.对于内存盘,不能设置FILESYSTEMIO_OPTIONS=setall,directio.

--//我的测试环境是建立在ramdisk上的,方法可以参考链接http://blog.itpub.net/267265/viewspace-1283884/

# mount | column -t | grep tmpfs

tmpfs on /dev/shm type tmpfs (rw)

tmpfs on /mnt/ramdisk type tmpfs (rw,size=8G)

--//当然如果重启机器,测试数据库就消失了,不过因为是测试,我保留一个冷备份在磁盘中.直接拷贝就ok了.

# find /mnt/ramdisk/book -name "*.*" -print0 | xargs -0 -I{} cachestats {}

/mnt/ramdisk/book/sysaux01.dbf pages in cache: 240642/240642 (100.0%) [filesize=962568.0K, pagesize=4K]

/mnt/ramdisk/book/tea01.dbf pages in cache: 10242/10242 (100.0%) [filesize=40968.0K, pagesize=4K]

/mnt/ramdisk/book/redo03.log pages in cache: 12801/12801 (100.0%) [filesize=51200.5K, pagesize=4K]

/mnt/ramdisk/book/redo02.log pages in cache: 12801/12801 (100.0%) [filesize=51200.5K, pagesize=4K]

/mnt/ramdisk/book/redo01.log pages in cache: 12801/12801 (100.0%) [filesize=51200.5K, pagesize=4K]

/mnt/ramdisk/book/users01.dbf pages in cache: 65538/65538 (100.0%) [filesize=262152.0K, pagesize=4K]

/mnt/ramdisk/book/control02.ctl pages in cache: 2612/2612 (100.0%) [filesize=10448.0K, pagesize=4K]

/mnt/ramdisk/book/control01.ctl pages in cache: 2612/2612 (100.0%) [filesize=10448.0K, pagesize=4K]

/mnt/ramdisk/book/undotbs01.dbf pages in cache: 275202/275202 (100.0%) [filesize=1100808.0K, pagesize=4K]

/mnt/ramdisk/book/temp01.dbf pages in cache: 104851/105986 (98.9%) [filesize=423944.0K, pagesize=4K]

/mnt/ramdisk/book/system01.dbf pages in cache: 194562/194562 (100.0%) [filesize=778248.0K, pagesize=4K]

/mnt/ramdisk/book/redostb04.log pages in cache: 12801/12801 (100.0%) [filesize=51200.5K, pagesize=4K]

/mnt/ramdisk/book/redostb03.log pages in cache: 12801/12801 (100.0%) [filesize=51200.5K, pagesize=4K]

/mnt/ramdisk/book/redostb02.log pages in cache: 12801/12801 (100.0%) [filesize=51200.5K, pagesize=4K]

/mnt/ramdisk/book/redostb01.log pages in cache: 12801/12801 (100.0%) [filesize=51200.5K, pagesize=4K]

/mnt/ramdisk/book/example01.dbf pages in cache: 88642/88642 (100.0%) [filesize=354568.0K, pagesize=4K]

# find /mnt/ramdisk/book -name "*.*" -print0 | xargs -0 -I{} cachedel {}