Oracle Database Tips by Donald Burleson

Installation of Oracle

Oracle installation is a complex topic. With the new CD-based installs, many of the platform dependencies dealing with installation have been reduced, but you as database administrator (DBA) need to be aware of the differences that apply to your platform. Usually, these differences will be explained in the release documents and platform-specific installation and user's guide provided with your software distribution. However, there are universal topics that involve structure and layout issues, and the purpose of this chapter is to present those topics and give you a general idea of the way to proceed with your installation.

1.1 Things to Consider Before Installation

Oracle Corporation has devised a standard architecture layout that it suggests should be used when installing Oracle. I have found that this standard layout, known as the Optimal Flexible Architecture or OFA for short, to be a logical way of laying out a database. OFA naming and layout standards should be used even in situations where the boundaries blur between disks, volumes, groups, and arrays, as is happening in the arena of RAID (redundant array of independent disks) technology. OFA should be used even when RAID5 or other RAID solutions are present because of the fact that it is a logical way to layout the database.

By using OFA you, and subsequent DBAs, can easily locate all files associated with the database. I have seen databases where OFA or an OFA-based arrangement weren't being used; files were placed anywhere it was convenient. This chaos method of database file placement led to bad backups due to missed files, deletion of files that were in use, and, because no one was tracking where files where placed, contention issues.

Optimal Flexible Architecture (OFA)

In accordance with Cary V. Millsap of the Oracle National Technical Response Team, the OFA process involves the following three rules:

1. Establish an orderly operating system directory structure in which any database file can be stored on any disk resource.

* Name all devices that might contain Oracle data in such a manner that a wild card or similar mechanism can be used to refer to the collection of devices as a unit.

* Make a directory explicitly for storage of Oracle data at the same level on each of these devices.

* Beneath the Oracle data directory on each device, make a directory for each different Oracle database on the system.

* Put a file X (X is any database file) in the directory /u??/ORACLE/sid/type_desig (or on W2K or NT: C:\oracle\sid\type_desig) if and only if X is a control file, redo log file, or datafile of the Oracle database whose DB_NAME is sid. The type_desig specifies the type of file to be placed in the directory at that location and is usually data, index, control or redo.

Tip

You may wish to add an additional directory layer if you will have multiple Oracle versions running at the same time. This additional layer includes the version level.

2. Separate groups of segments (data objects) with different behavior into different tablespaces.

* Separate groups of objects with different fragmentation characteristics in different tablespaces (e.g., don't put data and rollback segments together).

* Separate groups of segments that will contend for disk resources in different tablespaces (e.g., don't put data and indexes together).

* Separate groups of segments representing objects with differing behavioral characteristics in different tablespaces (e.g., don't put tables that require daily backup in the same tablespace with ones that require yearly backup).

3. Maximize database reliability and performance by separating database components across different disk resources. A caveat for RAID environments: Consider spreading datafiles across multiple controller volume groups.

* Keep at least three active copies of a database control file on at least three different physical arrays.

* Use at least three groups of redo logs in Oracle9i. Isolate them to the greatest extent possible on hardware serving few or no files that will be active while the RDBMS (relational database management system) is in use. Shadow redo logs whenever possible.

* Separate tablespaces whose data will participate in disk resource contention across different physical disk resources. (You should also consider disk controller usage.)

Minimum OFA Configuration

The minimum suggested configuration would consist of seven data areas: disks, striped sets, RAID sets, or whatever else comes down the pike in the next few years. These areas should be as separate as possible, ideally operating off of different device controllers or channels to maximize throughput. The more disk heads you have moving at one time, the faster your database will be. The disk layout should minimize disk contention. For example:

AREA1. Oracle executables and user areas, a control file, the SYSTEM tablespace, redo logs
AREA2. Data-datafiles, a control file, tool-datafiles, redo logs
AREA3. Index-datafiles, a control file, redo logs
AREA4. Rollback segment-datafiles
AREA5. Archive log files
AREA6. Export files
AREA7. Backup staging

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