About Creating an Oracle Database

After you plan your database using some of the guidelines presented in this section, you can create the database with a graphical tool or a SQL command. You typically create a database during Oracle Database software installation. However, you can also create a database after installation. Reasons to create a database after installation are as follows:

You used Oracle Universal Installer (OUI) to install software only, and did not create a database.
You want to create another database (and database instance) on the same host computer as an existing Oracle database. In this case, this chapter assumes that the new database uses the same Oracle home as the existing database. You can also create the database in a new Oracle home by running OUI again.
You want to make a copy of (clone) a database.

The specific methods for creating a database are:

With Database Configuration Assistant (DBCA), a graphical tool.

See "Creating a Database with DBCA"
With the CREATE DATABASE SQL statement.

See "Creating a Database with the CREATE DATABASE Statement"

Considerations Before Creating the Database

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 datafiles 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.

The following topics can help prepare you for database creation.

Planning for Database Creation
Meeting Creation Prerequisites

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.	Part II, "Oracle Database Structure and Storage" Part III, "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 datafiles 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 datafiles. 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.	Chapter 17, "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. See "Selecting a Character Set" for details.	Oracle Database Globalization Support Guide
Consider what 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.	Chapter 16, "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 and archived redo logs.	Chapter 12, "Managing the Redo Log" Chapter 13, "Managing Archived Redo Logs" Chapter 11, "Managing Control Files" Oracle Database Backup and Recovery User's Guide
Familiarize yourself with the principles and options of starting up and shutting down an instance and mounting and opening a database.	Chapter 3, "Starting Up and Shutting Down"

Selecting a Character Set

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.Even so, the default character set used by Oracle Universal Installer (OUI) and Database Configuration Assistant (DBCA) for the UNIX, Linux, and Microsoft Windows platforms is not AL32UTF8, but a Microsoft Windows character set known as an ANSI code page. The particular character set is selected based on the current language (locale) of the operating system session that started OUI or DBCA. If the language is American English or one of the Western European languages, the default character set is WE8MSWIN1252. Each Microsoft Windows ANSI Code Page is capable of storing data only from one language or a limited group of languages, such as only Western European, or only Eastern European, or only Japanese.A Microsoft Windows character set is the default even for databases created on UNIX and Linux platforms because Microsoft Windows is the prevalent platform for client workstations. Oracle Client libraries automatically perform the necessary character set conversion between the database character set and the character sets used by non-Windows client applications.You may also choose to use any other character set from the presented list of character sets. You can use this option to select a particular character set required by an application vendor, or choose a particular character set that is the common character set used by all clients connecting to this database.As AL32UTF8 is a multibyte character set, database operations on character data may be slightly slower when compared to single-byte database character sets, such as WE8MSWIN1252. Storage space requirements for text in most languages that use characters outside of the ASCII repertoire are higher in AL32UTF8 compared to legacy character sets supporting the language. The increase in storage space concerns only character data and only data that is not in English. The universality and flexibility of Unicode usually outweighs these additional costs.

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 version 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.

Meeting Creation Prerequisites

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.