Oracle Installation and Database Development On UNIX and Windows Platforms – A comparison

UNIX Windows NT/2000/XP
On UNIX, several files and scripts in different directories are used to start an instance automatically. Other scripts are run on computer shutdown, allowing applications such as Oracle to shut down cleanly For automatic startup on Windows, set registry parameter ORA_SID_AUTOSTART to true using an Oracle tool such as ORADIM.For automatic shutdown on Windows, set registry parameters ORA_SHUTDOWN and ORA_SID_SHUTDOWN to stop the relevant OracleServiceSID and shut down. Set registry parameter ORA_SID_SHUTDOWNTYPE to control shutdown mode (default is i, or immediate).
UNIX provides sophisticated control mechanisms for background processing and batch jobs. CRON, at, nohup etc are used For similar functionality on Windows, use the AT command. Add Task Utility is used to schedule jobs. There are lots of GUI tools also
On UNIX, utilities such as sar and vmstat are used to monitor Oracle background and shadow processes. These utilities are not integrated with Oracle. Performance utilities available on Windows include Oracle Performance Monitor, Task Manager, Control Panel, Event Viewer, User Manager, and Microsoft Management Console (included only 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 Windows Performance Monitor, except it has been preloaded with Oracle9i database performance elements.

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

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

On UNIX, Oracle uses the O_SYNC flag to bypass the file system buffer cache. The flag name depends on the UNIX port. On Windows, Oracle bypasses the file system buffer cache completely.
Shared libraries on UNIX are similar to shared DLLs on Windows. Object files and archive libraries are linked to generate Oracle executables. Relinking is necessary after certain operations, such as installation of a patch. On Windows, Oracle DLLs form part of the executable at run time and are therefore smaller. DLLs can be shared between multiple executables. Re-linking by the user is not supported, but executable images can be modified using ORASTACK utility.Modifying executable images on Windows reduces the chances of running out of virtual memory when using a large SGA or when supporting thousands of connections. However, Oracle Corporation recommends doing this only under the guidance of Oracle Support Services.

 

Backup strategy on UNIX is as follows: put the tablespace into backup mode, copy the files to the backup location, and bring the tablespace out of backup mode. Windows supports the same backup strategy, but you cannot copy files in use with normal Windows utilities. Use Oracle utility OCOPY to copy open database files to another disk location. Then use a utility to copy the files to tape.
On UNIX, you can specify more than one database writer process with initialization parameter DB_WRITERS. Multiple database writers can help, for example, when a UNIX port does not support asynchronous I/O. DB_WRITERS is supported but typically unnecessary on Windows, which has its own asynchronous I/O capabilities.
UNIX uses the concept of a DBA group. The root account cannot be used to install Oracle. A separate Oracle account must be created manually. On Windows, Oracle must be installed by a Windows username in the Administrators group. The username is automatically added to the Windows local group ORA_DBA, which receives the SYSDBA privilege. This allows the user to log in to the database using CONNECT / AS SYSDBA and not be prompted for a password.

Password files are located in the ORACLE_BASEORACLE_HOMEdatabase directory and are named pwdSID.ora, where SID identifies the Oracle9i database instance.

To InstallSet 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

To InstallLogin as a user with Administrative Privileges and do the installation.
The resources provided by the UNIX 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 On Windows, fewer resources are needed for interprocess communication (IPC), because the Oracle relational database management system is thread-based and not process-based. These resources, including shared memory and semaphores, are not adjustable by the user.
On UNIX, Oracle uses a process to implement each of such background tasks as database writer (DBW0), log writer (LGWR), shared server process dispatchers, and shared servers. Each dedicated connection made to the database causes another operating system process to be spawned on behalf of that session. On Windows, each background process is implemented as a thread inside a single, large process. For each Oracle database instance or system identifier, there is one corresponding process for Oracle9i database. For example, 100 threads inside one process on Windows handle 100 Oracle processes for a database instance on UNIX.All Oracle background, dedicated server, and client processes are threads of the master ORACLE Windows process, and all threads of the ORACLE process share resources. This multithreaded architecture is highly efficient, allowing fast context switches with low overhead.

To view processes or end individual threads, use Oracle Administration Assistant for Windows.

Choose Start > Programs > Oracle – HOME_NAME > Configuration and Migration Tools > Administration Assistant for Windows. Right-click the SID and choose Process Information.

UNIX supports raw partitions (logical drives). There is no limitation on the number of disk drives. Windows is limited to using drive letters A-Z, but creating raw partitions lets you bypass the disk drive limitation and divide disks into smaller sections.Use Windows NT Disk Administrator 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 database files.

An extended partition avoids the four-partition limit on Windows by allowing you to define large numbers of logical partitions to accommodate applications using Oracle9i database. Logical partitions can then be given symbolic link names to free up drive letters.

 

Services

Windows services are similar to UNIX daemons.

 

Oracle registers a database instance as a service (OracleServiceSID). Services start background processes.

To connect to and use an Oracle instance, an Oracle service is created during database creation 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.

 

The only service that needs to be running to be able to work with a database locally is the OracleServiceORCL service (where ORCL is the SID). This service will also automatically start up and shut down the database (using shutdown abort). If you installed a database, the default startup type will be Automatic. If you’re primarily accessing a remote database, you can switch this to Manual startup type.

 

With Oracle 8i, when a database is created there is only one service that is created.

Before that two services one for Oracle SID Service and the other for Oracle SID Start service.

 

The following Services are created when Oracle 9iR2 is installed in full

 

OracleOraHome92HTTPServer

OracleOraHome92TNSListener

OracleOraHome92ClientCache

OracleOraHome92ManagementServer and

OracleOraHome92Agent (the Intelligent Agent) When OEM OMS installed

OracleOraHome92SNMPPeerEncapsulator

OracleOraHome92SNMPPeerMasterAgent

OracleOraHome92PagingServer

OracleMTSRecoveryService

OracleWebAssistant0

 

The OracleOraHome92HTTPServer service (where OraHome92 is the name of the Oracle Home) is the Apache server that you automatically install when you install Oracle. You generally only need it to access Web pages in the Oracle Apache directories, such as JSP and modplsql pages.

 

The OracleOraHome92TNSListener service is only needed if the database will be accessed remotely (either from another host or locally via a SQL*Net network protocol). You can access local databases without this service.

 

The OracleOraHome92ClientCache service caches Oracle Names data for connecting to remote databases. This service is normally configured for Manual startup type. However, it isn’t necessary to run this service unless you have an Oracle Names server running somewhere.

 

There are four more services that are necessary for the Oracle Enterprise Manager: OracleOraHome92Agent (the Intelligent Agent), which monitors the database and Enterprise Manager requests and defaults to an Automatic startup type. OracleOraHome92SNMPPeerEncapsulator and OracleOraHome92SNMPPeerMasterAgent, which handle the Secure Network Management Protocol service. OracleOraHome92PagingServer, which sends alerts out through an alphanumeric pager via a modem or e-mail.

 

The OracleMTSRecoveryService, which is optional, allows your database to be used as a resource manager for the Microsoft Transaction Server, COM/COM+ objects, and transactions in a distributed environment.

 

If you only use your database occasionally, you can create simple batch jobs to start up and shut down your database with a double-click, without going through the graphical interface.

 

The following command can be used to generate a batch file for startup and shutdown of the services if you do not wish to use the GUI