Content Manager: What is LAN Cache?
Published 22 December 2003
Authors: Wei-Dong Zhu
This document describes the LAN Cache feature in Content Manager.
LAN Cache is an area of temporary storage on a local Resource Manager that contains a copy of objects stored on a remote Resource Manager. It provides application-transparent caching, using local servers as defined by the system administrator. This improves content retrieval times for geographically dispersed end users in a Content Manager configuration with multiple Resource Managers.
A user’s default Resource Manager should be the physically closest Resource Manager or the Resource Manager with the highest bandwidth network connection to the user. If the requested resource object is not cached on the Resource Manager, then the original is sent to the requestor from the Resource Manager on which it is stored and a second copy is sent to the user’s default Resource Manager. If the user or a colleague in the same location requests that resource object again, it can now be sent from the user’s local (default) Resource Manager.
LAN Cache can provide tremendous a benefit where there are relatively slow or busy network links between locations, and users need the same item multiple times. If the user only accesses the item once, then there is unnecessary network load generated sending a second copy to the Resource Manager that will never be used.
For configurations with geographically distributed users and multiple Resource Managers, LAN Cache can improve system response time for end users by caching commonly retrieved objects on a nearby Resource Manager and avoiding repeated high network latency requests to a remote Resource Manager.
When you enable LAN Cache and attempt to retrieve a cached object, the Resource Manager compares the timestamp applied when the object was originally retrieved to the timestamp of the object on the remote server. If the timestamps are different, the Resource Manager retrieves the updated object and overwrites the original cached object. For example, your system has three client users who are working on an insurance claim. Each user needs to view the same large photograph of a damaged car. The photograph (which is in the .TIFF file format) is stored on a content server in a different state. If LAN Cache is not enabled, each user requests and receives the file from the remote server to the client machine. Depending on file size and network traffic, the retrieval and display process can be slow and could reduce efficiency of the client users. With LAN cache enabled, each user receives a copy of the object stored on the local Resource Manager.
LAN Cache can be enabled from the New Resource Manager Definition window or Resource Manager Properties window in the System Administration Client.
This material has not been submitted to any formal IBM test and is published AS IS. It has not been the subject of rigorous review. IBM assumes no responsibility for its accuracy or completeness. The use of this information or the implementation of any of these techniques is a client responsibility and depends upon the client's ability to evaluate and integrate them into the client's operational environment.
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