Optimizing access to memory pages in software-implemented global page cache systems

This article is based on a thesis “Techniques of organizations shared access to distributed memory pages in cloud computing systems”, defensed in Igor Sikorsky Kyiv Polytechnic Institute in 2017. The paper describes distributed pages processing in Oracle Real Application Clusters (Oracle RAC) and compares it with other known processing methods. The comparison comprises analysis of different architectures (including shared nothing, shared disk and “based on a replication” architecture) in the context of SQL query processing and asserts reasonableness of distributed pages approach (also known as Global Cache Fusion) choice for cloud DBMS. As a result researching the Global Cache Fusion approach there was revealed main drawback of Oracle RAC systems - “increasing queue problem”: impossibility process requests after intensity of requests exceeds threshold intensity, which is inversely proportional packet sent time between nodes. To eliminate “increasing queue problem” during distributed page access the new access method is proposed, which is based on the initiation of one more page state - the "unloading" state, which increases the efficiency of processing distributed pages by reducing the number of transfers between nodes during hot page processing. The considered method can be used not only in cloud DBMS but also in other cloud systems in a case if they use page-organized distributed memory architecture.