Image Server API

Image Server is designed for handling the storage Storage and retrieval Retrieval of documents in WAN environment. It stores documents using File System and maintains information about these documents in the database. Image sServer thereby has two essential components namely,viz.

§ Image Cabinet – This is the database component of Image Server. It maintains information of all documents stored in the Image Server. This information includes location and size of document and other attributes relevant to mapping to actual document on File System.

§ Storage Management Server (SMS)– This component is the Socket-Server, which that listens to the requests from Image sServer and consequently, performs document addition or retrieval operation. on request.

Image Server provides a cClient iInterface, which that communicates with both the Image Cabinet and SMS and performs the operation on both as a single atomic operation.

Image Sserver consists of 3 basic building blocks. These building blocks define the architecture of Storage Management System. These building blocks are

§ Site

§ VolumeVolume

§ VolBlock

The logical containment can be defined as – a Site being a collection of volumeVolumes and a volumeVolume in turn being a collection of volblockVolBlocks.

A Site refers to SMS Sserver. A volumeVolume is a logical unit, which that can have multiple volblockVolBlocks.

Image storage Storage at a particular siteSite is divided into logical Logical sStorage uUnits called Image VolumeVolumes. An Image VolumeVolume is used to group several Image VolumeVolume Blocks where each Image Volume Block corresponds to a document data file that is a group of one or many document files concatenated.

The concatenated string of Site Id, Volume ID and VolBlockVolBlock ID in base 36 notationnotations and prefixed by PN forms the name of a document data file in which data of the volblockVolBlock is stored. This PN file provides the actual physical storage of documents. These files contain actual document together with the iImage cCabinet recovery information as hHeaders.

This iImage dData file is built by Image Server in correspondence to the Volume Block and provides the actual physical storage. The relationship about these entities Entities is illustrated in the figure given below.

In the above figure, Squares represent volumeVolumes, with the numbers in them indicating the volumeVolume Iindices. Each volumeVolume physically comprises of one or more volblockVolBlocks.

An iImage cCabinet can map to multiple siteSites but the vice versa is not truepossible. A siteSite is identified by its IP address Address and port Port noNumber. (It is recommended however to have only one SMS on one Sserver).

A volumeVolume can be replicated on multiple siteSites for backup. The primary siteSite on which volumeVolume is added is known as Home SiteSite and the siteSites where the volumeVolume is replicated are called Replicate Sites. All documents stored in a volumeVolume in Home Site are also consequently stored on replication Sites. E.g.For example, iIn the above figure, volumeVolume 3 is replicated at at siteSite A, B and volumeVolume 4 is replicated at siteSite B and C. Suppose volumeVolume 3 was originally added on siteSite A and replicated on siteSite B then SiteSite A will be Home Site and siteSite B will be Replicate Site for that volumeVolume.

If aan Image Server Client connects to siteSite B, then Site B will be its Preferred Site and Site A and C are Remote Sites.

Now if a document of volumeVolume 3 or 4 is to be accessed, then it can be accessed from siteSite B aloneonly. This is called Local Access. But if a document of volumeVolume 1, 2 or 5 is to be accessed, then a Remote Access will have to be made to the respective Remote Site.

In order to perform image Image sServer operations, different support is available on different platforms. For Java platform, jar is there and for windows, DLL is there. In every function defined below first the description is related to jar and then for DLL. Image sServer API has been logically divided into various sections according to the functionality.