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Donald K. Burleson

Oracle RAC Tips

Work out the Raw Devices or CFS Files

Once we make a decision to use either the raw devices or the cluster file system files, we need to make a plan for setting up the necessary storage volumes and file systems. The RAC system requires a minimum set of files/raw devices for creating default tablespaces and setting the redo log files etc.

If we are going to use the DBCA utility to create the initial database, we need to meet certain requirements concerning the default schemas. We need to provide the raw devices or file systems to store them. Then we create the user-defined or business application-related schemas and tablespaces.

In the case of UNIX and Linux-oriented cluster platforms, most of the vendors provide some kind of volume manager or tool, which helps to create volumes of manageable size and layout at the host level. These volumes can be used by the RAC database as raw partitions. Optionally, when we have the facility of the cluster file system, we can make the file system and mount them. When we are planning to use the volumes as the raw partitions, we may have to plan and pre-create a large number of partitions with appropriate sizes. Fig 6.3 shows the relation between the storage volumes and how they are presented for the use of the RAC database.

A LUN is the concept of the usable disk. LUN stands for Logical Unit Number. It is a physical disk, as seen by the node or host. They are also called RAID logical drives. Once they are introduced into a disk group at the volume manager level, they become the basis for logical volume creation. Volumes are usable pieces carved out of the storage pool. When they are used by the database application, they are the raw partitions. When a file system is created on the volumes, they become mountable at the operating system level. Fig. 6.3 shows the connection between the storage structures.

Fig 6.3 Storage Volume Relations

In the case of a Windows platform, the Windows disk manager provides a facility to create raw partitions. When using the OCFS (Oracle Cluster File System) module, we can create OCFS file systems.

General Steps

Fig 6.4 shows the basic flow of the cluster configuration, installation of the Oracle software, and creation of the database. This involves a sequential process of tasks.

Fig 6.4 Installation of Oracle RAC and Database Creation

As shown in the above figure, successfully setting up a RAC environment and creating the database involves many phases. The initial phase includes the selection of the server platform and operating system. Subsequently, we need to decide how many nodes we want to have initially and what kind of interconnect products we want to use for the node communication. Pre-planning and gathering the relevant information is an important step. These overall steps can be grouped into three different phases as shown in Fig 6.5.

Fig 6.5 Multiple Phases of RAC Database Creation

For more information, see the book Oracle 11g Grid and Real Application Clusters 30% off if you buy it directly from Rampant TechPress . 

Written by top Oracle experts, this RAC book has a complete online code depot with ready to use RAC scripts.  



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