Choosing the name
Before you create an Oracle database, you must choose a name for it as well as for the Oracle instance which will mount and open it. We recommend that the database name and the instance name be the same, unless you are running Oracle Parallel Server. In that case, we recommend choosing a database name and appending the instance number to it to form a unique name for each instance. For more information about the database and the instance, see Chapter 10, and Chapter 11.
While the names can be somewhat arbitrary, it is usually best to choose meaningful names—this will pay dividends later. The instance name must be unique on the host machine (that is, if you run more than one Oracle instance on a single machine, each must have a different name) for the following reasons:
Oracle appends the instance name to a standard prefix in order to create known filenames that are used by default. For example, the default name for the initialization file is created by adding the instance name to the prefix INIT. So, if the instance name is TEST, then Oracle will expect an initialization file called initTEST.ora (unless the pfile parameter is explicitly specified when starting the instance). The alert log filename is generated in a similar manner: the alert file for the TEST instance will be alert_TEST.log.
On most platforms, the internal process names used for the background processes are created by appending the instance name to a standard process name. For example, the PMON process for the TEST instance will be ora_pmon_TEST on a Unix system.
While it is not required, we recommend that database and corresponding instance names be unique across your entire enterprise in order to eliminate later confusion. We also recommend that names be four characters long, because Oracle appends the instance name to a standard prefix to create known filenames, and some operating systems have an eight-character filename limit.
Tip
The database and instance names are case sensitive on most platforms, so TEST is not the same as test or Test.
The database name is specified in the CREATE DATABASE command and in the DB_NAME parameter in the INIT.ORA file. These names must match. The instance name is specified in an operating system specific manner, usually using an environment variable. Table 2.1 shows where the instance name is defined for some popular systems.
|
Operating System |
Instance Name Comes From |
|
Windows (pre-95) |
ORACLE_SID environment variable |
|
Windows 95/98 |
ORACLE_SID entry in the registry |
|
Windows NT |
ORACLE_SID entry in the registry |
|
Unix |
ORACLE_SID environment variable |
|
VMS |
ORASID logical name |