Network Status Monitor Daemon (NSMD)

The Network Status Monitor (NSM) is a stateful NFS service that provides applications with information about the status of network hosts. The Network Lock Manager (NLM) daemon heavily uses the NSM to track hosts that have established locks as well as hosts that maintain such locks.

There is a single NSM server per host. It keeps track of the state of clients and noti®es any interested party when this state changes (usually after recovery from a crash).

The NSM daemon keeps a notify list that contains information on hosts to be informed after a state change. After a local change of state, the NSM noti®es each host in the notify list of the new state of the local NSM. When the NSM receives a state change noti®cation from another host, it will notify the local network lock manager daemon of the state change.

Network Lock Manager Daemon (NLMD)

The Network Lock Manager (NLM) daemon is a stateful service that provides advisory byte-range locking for NFS ®les. The NLM maintains state across requests, and makes use of the Network Status Monitor daemon (NSM) which maintains state across crashes (using stable storage).

The NLM supports two types of byte-range locks:

1.Monitored locks. These are reliable and helpful in the event of system failure. When an NLM server crashes and recovers, all the locks it had maintained will be reinstated without client intervention. Likewise, NLM servers will release all old locks when a client crashes and recovers. A Network Status Manager (NSM) must be functioning on both the client and the server to create monitored locks.

2.Unmonitored locks. These locks require explicit action to be released after a crash and re-established after startup. This is an alternative to monitoring locks, which requires the NSM on both the client and the server systems.

 

AS/400 as a Network File System Client

 

Several entities work together to communicate with the server and local jobs on the

 

NFS client. These processes are the following:

v RPC Binder Daemon. This daemon communicates with the local and remote

daemons by using the RPC protocol. Clients look for NFS services through this

daemon.

 

v Network Status Monitor and Network Lock Manager. These two daemons are

 

not mandatory on the client. Many client applications, however, establish

 

byte-range locks on parts of remote ®les on behalf of the client without notifying

 

the user. For this reason, it is recommended that the NSM and NLM daemons

 

exist on both the NFS client and server.

v Block I/O daemon. This daemon manages the data caches and is therefore

stateful in operation. It performs caching, and assists in routing client-side NFS

requests to the remote NFS server. Multiple instances of this daemon can

perform tasks simultaneously.

 

v Data and attribute caches. These two caches enhance NFS performance by

 

storing information on the client-side to prevent a client/server interaction. The

 

attribute cache stores ®le and directory attribute information locally on the client,

 

while the data cache stores frequently used data on the client.

Chapter 2. The Network File System Client/Server Model 11

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IBM AS/400E AS/400 as a Network File System Client, Network Status Monitor Daemon Nsmd, Network Lock Manager Daemon Nlmd
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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.
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