Operating system is a software that lets applications and other software to communicate with computer hardware. Consider operating system as a layer on top of hardware. All other software runs on top of the operating system.

Operating system provides basic services to applications.
,br> Example includes file sharing, support for network connections etc. Examples of operating systems on which SAP software could run include:

Microsoft Windows Server, Red Hat Linux, Suse Linux, HP-UX Unix, AIX, Solaris, OS400, z/OS.

Solaris is a UNIX version for Sun machines.HP-UX UNIX is a UNIX for HP machines

OS400 is an operating system that runs on IBM’s AS/400 machines.

Z/OS is an operating system that runs on mainframe machines.

Microsoft Windows Server, Red Hat Linux, and Suse Linux could be installed on x64 (Intel/AMD CPU) machines.

Following factors should be considered when deciding which Operating System to use with SAP.

• Current skill set of IT staff, cost of retraining, and cost of hiring new staff
• Support from operating system vendors
• Confidence on the Operating System and the vendor
• Verifiable client references
• Relationship of operating system vendor with SAP

Starting 2007, SAP software is only supported on 64-bit operating systems. 64-bit hardware is more prevalent. The demand for 32-bit hardware and therefore 32-bit operating system is reducing with time. For SAP systems, only 64-bit hardware should be considered unless you have good reasons to support older versions of SAP or some other related software that only runs on 32-bit environment.

When making a decision on which Operating System to use with your SAP system, you should keep in mind following features:

• Memory Management
• Crash Recovery
• Patch Management
• Security
• Clustering Capabilities
• Support for third party management utilities
• Presence of built-in management utilities

It may or may not be compatible with your IT department's vision to invest in new toolsets. In that case you also have to make sure that your existing monitoring applications, virus scanning software and backup solutions would work with this operating system.

On UNIX and Linux OS, SAP is installed on the directory:

/usr/sap
On Windows SAP resides in:
x:\usr\sap
Where x is a drive letter.

On windows the folder x:\usr\sap is shared as SAPMNT.

You can access this folder from other machine as \\machinename\sapmnt

where machine name is the name or IP address of the machine hosting SAP.

If you have multiple SAP instances on Windows machine then all instances must be installed under the same directory SAPMNT.

On all OS, UNIX, Linux, and Windows the next directory level is SID.

SID stands for SAP system identifier.