目錄，是圖書館所典藏資訊的索引，乃提供「閱聽者」、「資訊」間產生連結的定位指引。雖然目錄隨著資訊科技發展而愈趨易用，但是，研究者在平日使用圖書館服務的經驗中，仍不時遭遇到無法正常連接、存取公用目錄系統的窘狀。作為館藏資源的定位指引，圖書館公用目錄系統的可用率，對於圖書館服務品質之影響，不可謂不大。

本研究乃是為圖書館公用目錄擬定高可用率機制，並提出一有效之實作品。研究者經文獻探討，發現「冗餘配置」為眾多高可用率解決方案的共通手段。而在部署成本的考量下，研究者發現圖書館界、數位典藏界的OAI-PMH後設資料獲取機制是既有方案中最容易實作、使單位間透過網路「互助互備」達成「多點複本」冗餘配置的良好架構。

但是，對於處理實體館藏來說，OAI-PMH仍有所不足，是故研究者分別透過「版本控制」、「精簡化的書目、館藏紀錄格式」、「資料壓縮」等手段，壓低處理實體館藏書目、館藏紀錄資料在擷取、更新時的資源消耗，提出一份參考自OAI-PMH的改良架構，並據以實作出一套系統，證實其概念的確可行。

Catalog is an essential component of library services for patrons to find and identify the information what he or she needs. Though catalog usability is improved by information technologies, sometimes we are still encounter difficulties to access online public access catalogs (OPAC) while they are down or offline. As an index of library holdings, the availability of OPAC is an important factor of the library service quality.

This study is to design a facility to achieve high availability of OPAC and to implement a functional system. In our literature review, we find that redundancy is a common practice in high availability solutions. Concerning about the cost of the system deployment, we choose OAI-PMH as a reference model to build up a "cooperate redundancy" networking.

However, OAI-PMH is not suitable for processing real holdings in some aspects, thus we are by using "revision controlling", "compacted bibliography and holding metadata" and "data compressing" ways to downsize the bandwidth consuming while transferring real holdings metadata. Finally we are introducing our system design and its possible deploy networking topologies.

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