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Oracle8i Differences between Windows NT and UNIX

Services 

UNIX daemons are similar to services on Windows NT. 

Oracle registers a database instance as a service (OracleServiceSID).

To connect to and use an Oracle instance, an Oracle service is created during the database creation process and associated with the Oracle database. Once a service is created with the Oracle database, the service can run even while no user is logged on. This feature enables server security while running the Oracle database.

To Access Services:

By default, services run under the SYSTEM account.

1. Choose Start > Settings > Control Panel > Services to access the Services dialog box.

   OracleServiceSID and other Oracle services appear here.

Processes and Threads

See: Online Help for Oracle Administration Assistant for Windows NT  

Each Oracle background process exists as a separate process, for example, ora_dbw0_V816. 

All Oracle background, dedicated server, and client processes are threads of the master ORACLE process.

All the threads of the ORACLE process share resources on Windows NT. This multithreaded architecture is highly efficient, allowing fast context switches with low overhead.

To View Processes:

Use the Oracle Administration Assistant for Windows NT to view processes or kill individual threads.

1. Choose Start > Programs > Oracle - HOME_NAME > Database Administration > Oracle Administration Assistant for Windows NT.

2. Right-click the SID, for example V816, and choose Process Information.

Note: The Microsoft Management Console (MMC) is launched when the Oracle Administration Assistant for Windows NT is started on Windows NT 4.0. Oracle Corporation has integrated several database administration snap-ins into the MMC. 

File Sizes 

UNIX file system (UFS) or journalled file system (JFS). Maximum file size supported by most vendors is now 32 GB.

The Oracle block sizes vary between 2-8K. 

Oracle can be installed on FAT and NTFS file systems. By default, Oracle runs under the SYSTEM account, which does not have access to NTFS volumes, unless it is granted.

The maximum file size for FAT is 4 GB; for NTFS, 16 Exabytes (EB).

The Oracle block size is 8K. The maximum number of blocks per data file is 4 million. The maximum number of data files per database depends on block size.

When calculating database limits, the total maximum capacity of the database remains the same regardless of the way the bits are split up. 

Initialization Parameters: Multiple Database Writers 

You can specify more than one database writer process with the initialization parameter DB_WRITERS.

Multiple database writers can help, for example, when a UNIX port does not support asynchronous I/O. 

DB_WRITERS, which writes dirty buffers to disk, is not supported. Windows NT supplies its own I/O slaves and uses them to see if I/O is complete.

Multiple DB_WRITERS might cause synchronization problems.  

Direct Writes to Disk

See: Oracle8i Concepts

On both platforms, bypassing the file system buffer cache ensures the data is written to disk.  

Oracle uses the O_SYNC flag to bypass the file system buffer cache. The flag name depends on the UNIX port. 

Oracle bypasses the file system buffer cache completely. 

Memory Resources

See: Oracle8i Concepts 

The resources provided by the default kernels are often inadequate for a medium or large Oracle database.

The maximum size of a shared memory segment (SHMMAX) and maximum number of semaphores available (SEMMNS) may be too low for Oracle recommendations. 

Fewer resources are needed for interprocess communication (IPC) because the operating system is thread-based and not process-based. These resources, including shared memory and semaphores, are not adjustable by the user. 

Install Accounts and Groups 

Uses the concept of a DBA group. The root account cannot be used to install Oracle. A separate Oracle account must be created manually. 

Oracle must be installed by a Windows NT user name in the Administrator's group. The user name is automatically added to the Windows NT local group ORA_DBA, which receives SYSDBA the privilege. This allows the user to log into the database with the INTERNAL account and not be prompted for a password.

Password Files:

Password files are located in the ORACLE_BASE\ORACLE_HOME\DATABASE directory and are named PWDSID.ORA, where SID identifies the Oracle8i database instance. 

Dynamic Link Libraries (DLLs)

See: Oracle8i Concepts 

Shared libraries are similar to the shared DLLs on Windows NT. Object files and archive libraries are linked to generate the Oracle executables. Relinking is necessary after certain operations, such as installation of a patch. 

Oracle DLLs form part of the executable at run time, and, therefore, are smaller. DLLs can be shared between multiple executables. Relinking by the user is not supported, but executable images can be modified using the ORASTACK utility.

Modifying Executable Images:

Modifying executable images on Windows NT reduces the chances of running out of virtual memory when using a large SGA or an SGA with thousands of connections. However, Oracle Corporation recommends doing this under the guidance of Oracle Support Services. 

Installation

See: Oracle8i Client Installation Guide for Windows 

Many manual setup tasks required on UNIX are not required on Windows NT. 

You do not need to manually:

• set environment variables

• create a DBA group for database administrators

• create a group for users running Oracle Universal Installer

• create an account dedicated to installing and upgrading Oracle components

Multiple Oracle Homes and OFA

Using multiple Oracle homes and Optimal Flexible Architecture (OFA) provides many advantages when administering large databases. OFA is implemented on Windows NT and UNIX in the same way. However, differences exist with regard to the following:

• The top-level names of the OFA directory tree differ between Windows NT and UNIX. However, the main subdirectory and file names are the same on both operating systems.

• ORACLE_BASE directory.

• No support for symbolic links on Windows NT.

See: Chapter 3, "Multiple Oracle Homes and Optimal Flexible Architecture" 

Multiple Oracle homes on Windows NT is comparable to installation capabilities on UNIX. Environment variables can be set to specify Oracle homes. ORACLE_BASE is associated with a UNIX user's environment.

Symbolic Links

Symbolic links are supported. Although everything seems to be in one directory on the same hard drive, files can be on different hard drives if they are symbolically linked or have that directory as a mount point. 

ORACLE_HOME directories can be located under a single ORACLE_BASE directory. ORACLE_BASE is defined in the registry (for example, in HKEY_LOCAL_MACHINE \SOFTWARE\ORACLE\HOME0). Do not set ORACLE_HOME in the environment (software run from another Oracle home will not work reliably). In fact, beginning in release 8.1.6, the Oracle Universal Installer will reset it.

The goal of OFA is to place all Oracle software under one ORACLE_BASE directory and to spread the files across different physical drives as your databases increase in size. Oracle Corporation recommends that you use one logical drive to store your database administration files and that you place other files, as needed, on other logical drives in an ORADATA\DB_NAME directory.

For example, for a database named PROD, there are four logical drives:

• C:\ contains an Oracle home and the database administration files.

• F:\ contains the redo log files. (The F:\ drive could also represent two physical drives that have been striped to increase performance.)

• G:\ contains one of the control files and all of the tablespace files. (The G:\ drive could also use a RAID Level-5 configuration to increase reliability.)

• H:\ contains the second control file.

Symbolic Links

Symbolic links like those on UNIX are not supported, although Microsoft has announced the intention to support them in a near-future release. 

Automatic Startup/Shutdown 

Automatic Startup

Several files and scripts in different directories are used to start an instance automatically.

Automatic Shutdown

Scripts are run on computer shutdown, allowing applications such as Oracle to be shut down cleanly. 

Automatic Startup

Set the registry parameter ORA_SID_AUTOSTART to TRUE (the default) using an Oracle tool such as ORADIM.

1. Enter the following with parameters at the MS-DOS command prompt:

   C:\> ORADIM PARAMETERS
   

2. To start the listener automatically, set the service startup type to automatic.

Automatic Shutdown

1. Set the registry parameters ORA_SHUTDOWN and ORA_SID_SHUTDOWN to stop the relevant OracleServiceSID and shut down.

2. Set the registry parameter ORA_SID_SHUTDOWNTYPE to control the shutdown mode (the default is I, or Immediate).

Diagnostic and Tuning Utilities

See: Chapter 2, "Database Tools Overview". 

Performance utilities are not included with the operating system. Utilities such as sar and vmstat are used to monitor Oracle background and shadow processes. These utilities are not integrated with Oracle.

Task Manager on Windows NT displays currently running processes and their resource usage, similar to the UNIX ps -ef command or OpenVMS SHOW SYSTEM. However, Task Manager is easier to interpret and the columns can be customized.  

Performance utilities include Oracle Performance Monitor, Task Manager, Control Panel, Event Viewer, the registry, User Manager, and Microsoft Management Console (only included with Windows 2000).

Oracle is integrated with several of these tools. For example:

• Oracle Performance Monitor displays key Oracle database information.

  This tool is the same in appearance and operation as the Windows NT Performance Monitor, except it has been preloaded with Oracle8i database performance elements.

• Event Viewer displays system alert messages, including Oracle startup/shutdown messages and the audit trail.

Raw Partitions 

Raw partitions are supported. 

Data files for tablespaces can be stored on a file system, or on raw partitions. A raw partition is a portion of a physical disk that is accessed at the lowest possible level.

Use the Windows NT Disk Administrator application to create an extended partition on a physical drive. An extended partition points to raw space on the disk that can be assigned multiple logical partitions for the database files.

An extended partition avoids the four-partition limit on Windows NT by allowing you to define large numbers of logical partitions to accommodate applications using the Oracle8i database. Logical partitions can then be given symbolic link names to free up drive letters.

Oracle Parallel Server

Raw partitions are necessary for the shared data files in an Oracle Parallel Server (OPS) environment, available on both UNIX and Windows NT. OPS, in which Oracle instances run on all nodes simultaneously, provides clustering and high availability.