Oracle Database 11 g - Online Public Access Catalog

410 CHAPTER 9 ■ STORAGE MANAGEMENTOracle Direct NFSOracle Database 10g introduced ASM by allowing direct IO to the database files. In OracleDatabase 11g, Oracle provides a similar enhancement to NFS. Oracle Database 11g pioneersthe database world with Direct Network File System (Direct NFS). Oracle Direct NFS is an NFSclient built directly into the database kernel. With Oracle Direct NFS, the database kernel performsall the tuning processes automatically. DBAs and system administrators are no longer responsiblefor being intimate with all the tuning parameters associated with NFS.Oracle RAC implementations on NFS are a common industry practice. Debates aboutimplementing RAC on NFS vs. ASM have become a hot topic among database architects. Thedebate centers on cost, performance, and manageability. NFS on appliances such as NetworkAppliance has become a trend for RAC implementations. The introduction of Oracle Database11g Direct NFS fuels the fire for NFS implementations.For improved NFS performance, Oracle recommends the Direct NFS client that ships withOracle Database 11g. Instead of using the operating system NFS client, you can access NFSversion 3 servers directly using an Oracle internal Direct NFS client. If Oracle’s Direct NFS isnot able to open the NFS server, Oracle will utilize the operating system’s NFS client as specifiedin /etc/fstab and post an error message in the alert log.Set Up Direct NFSOracle Direct NFS setup involves manipulating the oranfstab file. The oranfstab file can residein several locations. Oracle will always check the $ORACLE_HOME/dbs directory first. If the oranfstabfile does not exist, it will search in the /etc directory. If an oranfstab file does not exist, Oraclewill use the operating system /etc/mtab file. Oracle’s Direct NFS client looks for mount pointsettings in the following order:• $ORACLE_HOME/dbs/oranfstab• /etc/oranfstab• /etc/mtabIf there are duplicate entries in these files, Oracle Direct NFS client will use the first entryfound.To implement Oracle Direct NFS, an existing NFS mount point must already exist. Themount options for NFS are irrelevant since Oracle Direct NFS will override and configure settingsoptimally. The NFS mount options in the /etc/fstab file for this particular example are as follows:nas103:/apps/oracle/share /oradata nfsrw,bg,hard,nointr,rsize=32768,wsize=32768,tcp,actimeo=0,vers=3,timeo=600It is important to note that in order to enable Direct NFS, you must disable reserved portsettings on the NFS server.Oracle uses the Oracle Disk Manager (ODM) to control NFS. To enable Direct NFS, youmust replace the standard ODM driver with the ODM NFS library. For the client to work, youneed to shut down the database and create a symbolic link from the standard ODM library topoint to the NFS ODM library. Before you create the symbolic link, you will rename the original