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Oracle9i Release 2 Server Architecture and Implementation

This chapter describes the basic structures of the Oracle Server system architecture, as far as they are BS2000 specific.

The topics described include:

• basic structures

• Oracle Server implementation

• address space planning

• Oracle Server environment definition file

• the ORALOAD library

• Oracle Server options

• userid requirements

Basic Structures

The concepts of tasks (i.e. processes in Oracle terminology) and memory structures (areas) are not BS2000 specific.

See the chapter "Memory Structures and Processes" in the Oracle9i Concepts manual for detailed information.

Database Files and Log Files

One or more database files contain the data dictionary, the user data, and indexes.

The Oracle Server requires a minimum of two log files, which need not be the same size, although on BS2000/OSD, the recommended minimum is 5000 PAM blocks. Note that the size of a log file is set in BS2000 blocks and not Oracle Server blocks.

Other Oracle Server Files

Initialization File

The initialization file, INIT.ORA, contains a set of parameters which are read when an instance is started or stopped. See the Oracle9i Reference manual and the Oracle9i Server Administrator's Guide for more information on the initialization file.

Server Parameter File

The server parameter file (SPFILE) is a binary server-side initialization file which cannot be edited using a text editor. It is initially built from a traditional text initialization file using the CREATE SPFILE statement.

ORAENV File

Every Oracle Server utility and product uses the Oracle Server environment definition file which is referenced as ORAENV. This file contains the Oracle Server environment variables which are used to describe the operating environment for each Oracle Server task. The Database Administrator also uses the ORAENV file to define BS2000-specific parameters necessary for database configuration.

Control Files

These files contain the information required by the Oracle Server to identify the instance and are specified in the initialization file.

Message Files

Message texts are stored in table modules which are dynamically loaded from the ORAMESG library at execution time.

Oracle-Managed Files

File names for Oracle-managed files have the following format on BS2000:

File type	Format
Datafile	O1-MF-%t-%u0.DBF
Tempfile	O1-MF-%t-%u0.TMP
Redo log File	O1-MF-%g-%u0.LOG
Control File	O1-MF-%u0.CTL

where

%t
is the tablespace name. An underscore "_" in the tablespace name is converted into a hyphen "-" in the file name.

%u
is an eight character string that guarantees uniqueness

%g
is the online redo log group number

For detailed information see the chapter "Using Oracle-Managed Files" in the Oracle 9i Database Administrator's Guide.

Two-Task Mode

Before Oracle 9i, Oracle applications could run in single-task mode and in two-task mode. In Oracle 9i single-task mode is not available any more.

In two-task mode, a user task connects to a server task which executes Oracle Server code on behalf of the user task. The user task does not have access to the SGA. Communication between a user task and a server task is via Oracle Net Services.

Address Space Planning

The Oracle Server uses a number of data and code areas which must be at the same virtual addresses in all server and background tasks. Normally, the default values provided with the Oracle Server will be sufficient. Address space planning (explicit placement of the Oracle Server data areas) may be required, when user programs have address space layout requirements conflicting with the default Oracle Server values. Also, dynamic subsystems may occupy the default address ranges, which may require you to relocate the Oracle Server areas.

Oracle Server Data Area Placement

The following ORAENV variables control explicit placement of the Oracle Server data areas:

• COM_BASE

• KNL_BASE

• PGA_BASE

• SGA_BASE

The order of the areas in the address space is not significant. The xxx_BASE variable is evaluated only during STARTUP processing.

Once the database is started, users attaching to it do not need to specify the values in their ORAENV files, as they are automatically supplied with the common values during connection. This means that the settings in the user's ORAENV file are ignored. Figure 2-1 gives an example of the placement of data areas.

Text description of the illustration fig2-1.gif

Figure 2-1 Placement of Data Areas in Background, Server and User Tasks

The xxx_BASE values must be compatible with the BS2000/OSD value SYSBASE (defined by BS2000/OSD generation and delimiting the user´s adress space).

In general Oracle administrators should be aware of conflicts between Oracle pool placements and other pool placements in the system.

Oracle Server Environment Definition File

This section describes the ORAENV file, how it is used, and how you use the environment variables to specify the default database.

The ORAENV text file has the format of a BS2000 command procedure that issues a /SET-FILE-LINK ORAENV command to itself. Each line contains an Oracle Server environment variable and its assigned value. When reading this file, the Oracle Server ignores all lines which have a slash, "/" or an asterisk, "*" in column 1.

Generating ORAENV

The INSTALL.P.DBA procedure automatically creates a copy of the ORAENV file. This file provides a default configuration for an Oracle Server. You can edit this file to adapt it to local needs. Users can also generate an ORAENV file specific to their own environment. This is described in the chapter "Getting Started" in the Oracle9i for Fujitsu Siemens BS2000/OSD User's Guide.

ORAENV Variables

The appendix "ORAENV Variables" contains a list of ORAENV variables that the Database Administrator can use. Most users will only need to set a few of these variables. Any "database administrator-only" variables that are placed in a user's ORAENV file are ignored.

Running ORAENV

To set environment variables, simply issue a CALL-PROCEDURE command on the ORAENV file containing the environment variables for the database you want to use. The name of the ORAENV file is sid.P.ORAENV (where sid is the database system identifier). For example, to set the environment variables for database DEMO using the example ORAENV file, enter:

/CALL-PROCEDURE DEMO.P.ORAENV

You can also generate an ORAENV file and issue the /SET-FILE-LINK command before calling any Oracle Server program:

/SET-FILE-LINK ORAENV, filename

where filename is the name of a file having the same format as DEMO.P.ORAENV and which defines at least the ORASID environment variable.

Note the following:

• The Database Administrator should not modify their ORAENV file while the Oracle Server is running.

• A user may modify their ORAENV file at any time.

You can run several Oracle Server databases simultaneously on your system; even within the same Database Administrator account. A unique system identifier provides a globally unique "name" for the database so that a user can select a particular database by setting the ORASID environment variable. The user does this by activating the ORAENV file sid.P.ORAENV.

Whenever an Oracle Server product (for example, SQL*Plus) is started, it checks, if the linkname ORAENV is defined and reads the related file, storing the variable assignments for later use. If no linkname ORAENV is set (or the related file cannot be read), the sid remains undefined. Oracle Corporation recommends that a linkname ORAENV is always defined prior to a call to an Oracle Server program.

The ORALOAD Library

The ORALOAD library ($ORACL920.ORALOAD.LIB by default) is required to run any Oracle9i Release 2 program. The Oracle Server uses this library to load executables and subroutines dynamically when required. The linkname ORALOAD must identify the ORALOAD library before calling any Oracle Server program. If the linkname is missing, you get a BLS (BS2000/OSD loader) error message. Normally, this linkname is set when the ORAENV procedure is called.

The ORAMESG library

The ORAMESG library ($ORACL920.ORAMESG.LIB by default) is required for dynamically loading tables (such as message files) by a Oracle task when required. The linkname ORAMESG must identify the ORAMESG library before calling any Oracle program. If the linkname is missing, you get a BLS (BS2000/OSD loader) error message. Normally, this linkname is set when the ORAENV procedure is called.

Userid Requirements

Installation Userid (ORAUID)

The installation userid (referred to as ORAUID) functions as the program and model data library userid. During Oracle Server installation, the installation tape is read into this userid, which should be empty. The ORAUID includes:

• executable programs (such as SQL*Plus, the background and network programs)

• load libraries, from which modules are loaded during program execution (for example, the shared KERNEL module, the precompiler run-time modules), in particular ORALOAD.LIB

• message files

• other data files (like .SQL files for the DEMO tables)

• INCLUDE files, application demo files and system configuration files specifying default precompiler options for precompiler users

• object libraries required to link-edit precompiler applications (such as PRO.LIB)

• port-specific installation utilities (programs, command procedures, and so on)

A separate ORAUID is required for each separate Oracle Server release. However, multiple databases using the same version can, and should, refer to the same installation userid.

Authorizations and File Access Rights

This userid does not require any special BS2000 privileges.

• You must not use the BS2000/OSD System Administrator userid "TSOS" as an Oracle Server installation userid.

• The ORAUID does not require any specific /JOIN options.

• Only the installation phase requires a BS2000 LOGIN under this userid

• As this userid functions as a library userid, most files should be cataloged as follows:

  	  SHARE=YES,ACCESS=READ 
  

• You do not need to define "write" access for any file after executing INSTALL.P.ORACLE.

Default Name

The default name for the ORAUID is $ORACL920. If you select a different name during the installation of Oracle Server software, the procedure, INSTALL.P.ORACLE, which runs as part of the installation, makes the necessary changes to the installation files.

DBA Userid

The DBA userid is a BS2000 userid that is used as the owner of one or more of the Oracle Server databases. The database, the control and the data files for a specific Oracle Server database are all owned by this userid (and are all prefixed by the Oracle Server sid).

All tasks making up the running database, background tasks and server tasks started for two-task Oracle Server, execute under the DBA userid. These tasks refer to the executable programs and libraries which are available under the installation userid (ORAUID). These need not, and should not, be copied into the DBA userid. It is possible to use the installation userid (ORAUID) as a DBA userid. However, it is recommended that you use separate userids. The DBA userid can also be used as a normal userid.

Running SQL*Plus on the Local Machine

Multiple databases can be created under the same, or under different DBA userids. If installed under different BS2000 userids, the databases are separated and protected from each other, subject to the BS2000 protection mechanisms. In particular, a Database Administrator cannot administer a database running under a different BS2000 userid (there is no global DBA privilege in Oracle Server for BS2000/OSD).

Authorizations and File Access Rights

The DBA userid needs the more extensive /JOIN privileges to run an Oracle Server database. These privileges include:

• The right to start jobs immediately, preferably in a JOBCLASS reserved for Oracle Server background jobs. Failure to do this may cause delays when starting the database and when creating the two-task server.

• The right to start jobs with no time limit (TIME=NTL). Failure to do this may cause database tasks to abort.

• The right to set jobs to TP state. Failure to do this may reduce database performance.

• The right to set Common Memory Pools as read-only. Failure to do this may reduce shared-code security.

• The BS2000/OSD System Administrator userid "TSOS" should not under any circumstances be used as an Oracle Server DBA userid.

• File access rights set under the DBA userid should be:

  SHARE=NO, 
  
  ACCESS=WRITE 
  

Default Name

There is no default name for a DBA BS2000 userid.

Oracle Server-User Userids

An Oracle user accesses and uses the database via the Oracle utilities such as SQL*Plus, and via the precompiler application programs. The user can connect to an Oracle Server database through the Oracle Net Services facilities.

Concurrent access to the same and to different Oracle Server databases originating from multiple tasks running under the same BS2000 userid, is supported without any specific restrictions.

Concurrent access from multiple tasks running under different BS2000 userids is supported without restrictions.

The BS2000 userid can also be used as the Oracle Server connect userid by means of the "OPS$" generic facility.

Authorizations and File Access Rights

These userids do not require any special BS2000 privileges.

• No file owned by a normal user needs any specific access attributes, as Oracle Server programs access such files locally from within that userid. For example, LOGIN.SQL data files.

• No specific /JOIN privileges are needed.