2.2 Considerations Before Creating the Database

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Database creation prepares several operating system files to work together as an Oracle Database. You only need to create a database once, regardless of how many data files it has or how many instances access it. You can create a database to erase information in an existing database and create a new database with the same name and physical structure.

1. Planning for Database Creation


Prepare to create the database by research and careful planning.

Table 2-1 lists some recommended actions:
Table 2-1 Database Planning Tasks

 Action
Additional Information
Plan the database tables and indexes and estimate the amount of space they will require. Oracle Database Structure and Storage
Schema Objects 
Plan the layout of the underlying operating system files your database will comprise. Proper distribution of files can improve database performance dramatically by distributing the I/O during file access. You can distribute I/O in several ways when you install Oracle software and create your database. For example, you can place redo log files on separate disks or use striping. You can situate data files to reduce contention. And you can control data density (number of rows to a data block). If you create a Fast Recovery Area, Oracle recommends that you place it on a storage device that is different from that of the data files.
To greatly simplify this planning task, consider using Oracle Managed Files and Automatic Storage Management to create and manage the operating system files that comprise your database storage.
Using Oracle Managed Files
Oracle Automatic Storage Management Administrator's Guide
Oracle Database Performance Tuning Guide
Oracle Database Backup and Recovery User's Guide
Your Oracle operating system–specific documentation, including the appropriate Oracle Database installation guide.
Select the global database name, which is the name and location of the database within the network structure. Create the global database name by setting both the DB_NAME and DB_DOMAIN initialization parameters. "Determining the Global Database Name"
Familiarize yourself with the initialization parameters contained in the initialization parameter file. Become familiar with the concept and operation of a server parameter file. A server parameter file lets you store and manage your initialization parameters persistently in a server-side disk file. "About Initialization Parameters and Initialization Parameter Files"
"What Is a Server Parameter File?"
Oracle Database Reference
Select the database character set.
All character data, including data in the data dictionary, is stored in the database character set. You specify the database character set when you create the database.
Oracle Database Globalization Support Guide
Consider which time zones your database must support.
Oracle Database uses one of two time zone files as the source of valid time zones. The default time zone file is timezlrg_11.dat. It contains more time zones than the smaller time zone file, timezone_11.dat.
"Specifying the Database Time Zone File"
Select the standard database block size. This is specified at database creation by the DB_BLOCK_SIZE initialization parameter and cannot be changed after the database is created.
The SYSTEM tablespace and most other tablespaces use the standard block size. Additionally, you can specify up to four nonstandard block sizes when creating tablespaces.
"Specifying Database Block Sizes"
If you plan to store online redo log files on disks with a 4K byte sector size, determine whether you must manually specify redo log block size. "Planning the Block Size of Redo Log Files"
Determine the appropriate initial sizing for the SYSAUX tablespace. "About the SYSAUX Tablespace"
Plan to use a default tablespace for non-SYSTEM users to prevent inadvertently saving database objects in the SYSTEM tablespace. "Creating a Default Permanent Tablespace"
Plan to use an undo tablespace to manage your undo data. Managing Undo
Develop a backup and recovery strategy to protect the database from failure. It is important to protect the control file by multiplexing, to choose the appropriate backup mode, and to manage the online redo log and archived redo log files. Managing the Redo Log
Managing Archived Redo Log Files
Managing Control Files
Familiarize yourself with the principles and options of starting up and shutting down an instance and mounting and opening a database. Starting Up and Shutting Down


2. About Selecting a Character Set


It is important to select the right character set for your database. Oracle recommends AL32UTF8 as the database character set.

AL32UTF8 is Oracle's name for the UTF-8 encoding of the Unicode standard. The Unicode standard is the universal character set that supports most of the currently spoken languages of the world. The use of the Unicode standard is indispensable for any multilingual technology, including database processing.

After a database is created and accumulates production data, changing the database character set is a time consuming and complex project. Therefore, it is very important to select the right character set at installation time. Even if the database does not currently store multilingual data but is expected to store multilingual data within a few years, the choice of AL32UTF8 for the database character set is usually the only good decision. The universality and flexibility of Unicode typically outweighs some additional cost associated with it, such as slightly slower text processing compared to single-byte character sets and higher storage space requirements for non-ASCII text compared to non-Unicode character sets.

If you do not want to use AL32UTF8, and you are not restricted in your choice by a vendor requirement, then Oracle suggests that you use one of the character sets listed as recommended for the database. The recommended character sets were selected based on the requirements of modern client operating systems. Oracle Universal Installer (OUI) presents the recommended list only, and Database Configuration Assistant (DBCA) must be used separately to choose a non-recommended character set. In addition, the default database creation configuration in DBCA allows the selection of the recommended character sets only. You must use the advanced configuration mode of DBCA or the CREATE DATABASE statement to select a non-recommended character set.

Caution: Do not use the character set named UTF8 as the database character set unless required for compatibility with Oracle Database clients and servers in Oracle8i Release 1 (8.1.7) and earlier, or unless explicitly requested by your application vendor. Despite having a very similar name, UTF8 is not a proper implementation of the Unicode encoding UTF-8. If the UTF8 character set is used where UTF-8 processing is expected, data loss and security issues may occur. This is especially true for Web related data, such as XML and URL addresses.

Note: You can only select an ASCII-based character set for the database on an ASCII-based platform.

3. Meeting Creation Prerequisites


Prerequisites must be met before creating a database.

Before you can create a new database, the following prerequisites must be met:
  • The desired Oracle software must be installed. This includes setting various environment variables unique to your operating system and establishing the directory structure for software and database files.
  • Sufficient memory must be available to start the Oracle Database instance.
  • Sufficient disk storage space must be available for the planned database on the computer that runs Oracle Database.
All of these are discussed in the Oracle Database Installation Guide specific to your operating system. If you use the Oracle Universal Installer, it will guide you through your installation and provide help in setting environment variables and establishing directory structure and authorizations.

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