AS/400 as a Network File System Server

Representation (XDR) and then sent to the server using a socket. The simple User Datagram Packet (UDP) protocol actually communicates between client and server. Some aspects of NFS use the Transmission Control Protocol (TCP) as the base communication protocol.

The operation of NFS can be seen as a logical client-to-server communications system that speci®cally supports network applications. The typical NFS ¯ow includes the following steps:

1.The server waits for requests from one or more clients.

2.The client sends a request to the server and blocks (waits for a response).

3.When a request arrives, the server calls a dispatch routine.

4.The dispatch routine performs the requested service and returns with the results of the request. The dispatch routine can also call a sub-routine to handle the speci®c request. Sometimes the sub-routine will return results to the client by itself, and other times it will report back to the dispatch routine.

5.The server sends those results back to the client.

6.The client then de-blocks.

The overhead of running more than one request at the same time is too heavy for an NFS server, so it is designed to be single-threaded. This means that an NFS server can only process one request per session. The requests from the multiple clients that use the NFS server are put into a queue and processed in the order in which they were received. To improve throughput, multiple NFS servers can process requests from the same queue.

The NFS server is composed of many separate entities that work together to process remote calls and local requests. These are:

vNFS server daemons. These daemons handle access requests for local ®les from remote clients. Multiple instances of particular daemons can operate simultaneously.

vExport command. This command allows a user to make local directories accessible to remote clients.

v/etc/exports ®le. This ®le contains the local directory names that the NFS server exports automatically when starting up. The administrator creates and maintains this ®le, which is read by the export command. For more discussion about this ®le, see ª/etc/exports Fileº on page 94 and ªChapter 4. Server Exporting of File Systemsº on page 25.

vExport table. This table contains all the ®le systems that are currently exported from the server. The export command builds the /etc/exports ®le into the export table. Users can dynamically update the export table with the export command.

For discussion regarding the CHGNFSEXP (Change Network File System

Export) and EXPORTFS (Export File System) commands and how they work with both the /etc/exports ®le, see ªChapter 4. Server Exporting of File Systemsº on page 25.

Network File System Server-Side Daemons

Chapter 2. The Network File System Client/Server Model 9

AS/400E specifications

The IBM AS/400E, now more commonly known as IBM i, is a robust and versatile midrange server that has been designed to provide a comprehensive computing solution for businesses of all sizes. First introduced in the late 1980s, the AS/400 series has undergone multiple enhancements and rebranding, with the AS/400E being one of the notable iterations. This powerful platform is closely associated with IBM's commitment to reliability, scalability, and integrated business solutions.

One of the main features of the AS/400E is its highly integrated architecture that combines hardware and software into a cohesive system. This integration allows for seamless operations, reducing the complexity typically associated with managing disparate systems. The system is powered by IBM's proprietary OS/400 operating system, which has evolved into IBM i, featuring advanced capabilities like object-oriented programming, integrated database management, and security features that are essential for enterprise environments.

A key characteristic of the AS/400E is its robust database support, primarily through the use of DB2 for i. This integrated database management system enables efficient data handling and retrieval, facilitating real-time business analytics and reporting. Furthermore, the platform supports a variety of programming languages, including RPG, COBOL, and Java, making it flexible for developers who require diverse tools for application development.

The AS/400E is also known for its exceptional reliability and uptime, making it a preferred choice for critical business applications in industries such as finance, healthcare, and manufacturing. This reliability is backed by advanced error detection and correction mechanisms, as well as redundancy features that help prevent data loss and minimize downtime.

In terms of scalability, the AS/400E can effortlessly expand to accommodate growing business demands. Organizations can increase processing power by adding more resources without significant disruption. This scalability, combined with the system’s built-in virtualization capabilities, allows businesses to optimize resource usage and streamline operations.

Security is another defining feature of the AS/400E. The platform incorporates various layers of security measures, including user authentication, encryption, and comprehensive auditing capabilities, ensuring that sensitive business data is protected against unauthorized access.

Overall, the IBM AS/400E remains a powerful tool in the enterprise computing landscape, providing businesses with an integrated, reliable, and secure solution for their technological needs. Its enduring popularity is a testament to its capability to evolve with changing business requirements while maintaining its core attributes of high performance and stability.

IBM AS/400E manual AS/400 as a Network File System Server, Network File System Server-Side Daemons

Models: AS/400E