directories. For this reason, exporting /DEV or objects within it can cause

administrative difficulties. The next sections describe how you can work around one

such scenario.

 

Using User-De®ned File Systems with Auxiliary Storage Pools

 

This scenario involves an eager user, a non-communicative system administrator,

 

and a solution to an ASP problem through the Network File System.

 

A user, Jeff, accesses and works with the TULAB2 namespace each time he logs

 

into his account on a remote NFS client. In this namespace exist a number of

 

user-de®ned ®le systemsA.(udfs, B.udfs, C.udfs, and D.udfs) in an ASP

 

connected to the namespace as /DEV/QASP02/. Jeff is used to working with these

 

directories in their familiar form every day.

 

One day, the system administrator deletes the UDFSs and physically removes the

 

ASP02 from the server. The next time Jeff logs in, he can't ®nd his UDFSs. So,

 

being a helpful user, Jeff creates a /DEV/QASP02/ directory using the CRTDIR or

 

MKDIR command and ®lls the sub-directories with replicas of what he had before.

 

Jeff replaces A.udfs, B.udfs, C.udfs, and D.udfs with 1.udfs, 2.udfs, 3.udfs, and

 

4.udfs.

 

This is a problem for the network because it presents a false impression to the user

 

and a liability on the server. Because the real ASP directories (/DEV/QASPXX) are

 

only created during IPL by the system, Jeff's new directories do not substitute for

 

actual ASPs. Also, because they are not real ASP directories (/DEV/QASPXX), all of

 

Jeff's new entries take up disk space and other resources on the system ASP, not

 

the QASP02, as Jeff believes.

 

Furthermore, Jeff's objects are not UDFSs and may have different properties than

 

he expects. For example, he cannot use the CRTUDFS command in his false

 

/DEV/QASP02 directory.

 

The system administrator then spontaneously decides to add a true ASP without

 

shutting the system down for IPL. At the next IPL, the new ASP will be mounted

 

over Jeff's false /dev/qasp02 directory. Jeff and many other users will panic

 

because they suddenly cannot access their directories, which are ªcovered upº by

 

the system-performed mount. This new ASP cannot be unmounted using either the

 

RMVMFS or UNMOUNT commands. For Jeff and other users at the server, there is

 

no way to access their directories and objects in the false ASP directory (such as

 

1.udfs, 2.udfs, 3.udfs, and 4.udfs)

 

Recovery with the Network File System

The NFS protocol does not cross mount points. This concept is key to understanding the solution to the problem described above. While the users at the server cannot see the false ASP and false UDFSs covered by the system-performed mount, these objects still exist and can be accessed by remote clients using NFS. The recovery process involves action taken at both the client and the server:

1.The administrator can export a directory above the false ASP (and everything ªdownstreamº of it) with the EXPORTFS command. Exporting/DEV exports the underlying false ASP directory, but not the true ASP directory that is mounted over the false ASP directory. Because NFS does not cross the mount point, NFS recognizes only the underlying directories and objects.

Chapter 3. NFS and the User-De®ned File System (UDFS) 23

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IBM AS/400E manual Using User-Dened File Systems with Auxiliary Storage Pools, Recovery with the Network File System

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.