The Oracle Database 11g installation process has some changes in the way it specifies the Oracle base directory, Oracle home directory, and flash recovery area. Additionally, there is a new infrastructure called the Active Diagnostic Information Repository (Automatic Diagnostic Repository, ADR), which provides a unified location for all database diagnostic information.
1. Selecting the Oracle Base Directory Location
The Oracle base directory is the top-level directory for installing Oracle software. The OFA-recommended path for this directory is `/mount_point/app/`. For example, a typical Oracle base directory path would be `/u01/app/oracle`, where "oracle" is the owner of the Oracle software. It is recommended to set the Oracle base directory as an environment variable, similar to previous Oracle versions, though in the current version, it may become a mandatory variable. The Oracle Universal Installer now provides a list box to edit or select the Oracle base directory. The Oracle Universal Installer automatically derives the default Oracle home directory location from the Oracle base directory you provide. The Oracle home directory is a subdirectory of the Oracle base directory, which is where you install all your Oracle software. If you wish to specify another directory as the Oracle home directory, you can edit the directory location provided by the Oracle Universal Installer. Oracle recommends that you specify the same Oracle base directory for multiple Oracle home directories created for different users.
2. Choosing Data File and Flash Recovery Area Locations
In Oracle Database 11g, by default, all data files are located in a subdirectory under the Oracle base directory. The flash recovery area is also located in a subdirectory under the Oracle base directory. Oracle recommends creating the flash recovery area on a disk different from the one where the data files reside. In Oracle Database 10g, both the flash recovery area and data files were located in the Oracle home directory. In Oracle Database 11g, if you choose `/u01/app/oracle` as the Oracle base directory, the locations for data files and the flash recovery area should look like this:
```
/u01/app/oracle/oradta
/u01/app/oracle/flash_recovery_area
```
If you do not place the data files and the flash recovery area in different locations, the Oracle Universal Installer will issue a warning.
3. Automatic Diagnostic Repository (ADR)
The Automatic Diagnostic Repository (ADR) is a new feature in Oracle Database 11g that consolidates all diagnostic data, including various trace files. The purpose of ADR is to provide a single directory location for all error data required for diagnostics and problem-solving, thus enabling faster resolution of errors and troubleshooting. ADR is specified via the new initialization parameter `diagnostic_dest`. ADR replaces traditional diagnostic directories such as `bdump`, `cdump`, and `udump`. With traditional diagnostic directories, identifying necessary trace and error files during troubleshooting had to be done manually. ADR uses standardized methods to store diagnostic data for Oracle databases as well as other Oracle products. Then, specific automated diagnostic tools read this diagnostic data, providing shorter turnaround times for resolving issues with various Oracle products.
There are different directories under ADR, such as `cdump`, `alert`, etc. The alert log, which was previously viewed in Unix using the vi editor, is now an XML-based file. This file can be viewed using the new ADRCI command-line tool.
If you choose to use ADR, you must provide the base directory location for ADR to the Oracle Universal Installer. To consolidate diagnostic data, Oracle recommends selecting the same ADR directory for all Oracle products.
If `ORACLE_BASE` is not set, a warning will appear in the alert log, although `ORACLE_BASE` is a recommended environment variable, it will become a mandatory variable in future versions.
By default, the ADR base directory for storing diagnostic data is set to the Oracle base directory. However, you can set another directory for ADR by specifying the value of the new initialization parameter `diagnostic_dest`. The ADR directory name is `$ORACLE_BASE/diag`, which includes several subdirectories, with the most important being `rdbms`. In the `rdbms` directory, diagnostic files are organized by database name and instance name. For example, for a database named `orcl` with an instance name `orcll`, the trace files (including the traditional text format alert log) are located in the following directory (with the Oracle base directory being `/u01/app/oracle`):
```
/u01/app/oracle/diag/rdbms/orcl/orcll
```
As shown in this directory structure, diagnostic data for multiple databases (and other Oracle products) can be stored under the same ADR base directory.
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