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What is the role of the transaction manager and session?
The transaction manager co-ordinates database transactions and keeps a record of running and closed transactions. When transaction is rolled back or committed, the transaction manager notifies the involved storage engines about the event so they can run necessary actions.
Explain how you can avoid un-necessary logging information from being stored?
You can avoid un-necessary logging information from being stored by pausing the replication by stopping the schema-related jobs.
Define Five-minute rule?
It is a rule of thumb for deciding whether a data item should be kept in memory, or stored on disk and read back into memory when required. The rule is “randomly accessed disk pages of cache are re-used every 5 minutes”.
Waiting for data to be loaded from main memory into the CPU cache is called as Stall.
Describe SAP HANA Database Architecture in brief?
The SAP HANA database is developed in C++ and runs on SUSE Linux Enterpise Server. SAP HANA database consists of multiple servers and the most important component is the Index Server. SAP HANA database consists of Index Server, Name Server, Statistics Server, Pre-processor Server and XS Engine.
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Index server is the main SAP HANA database component
It contains the actual data stores and the engines for processing the data.
The index server processes incoming SQL or MDX statements in the context of authenticated sessions and transactions.
The database persistence layer is responsible for durability and atomicity of transactions. It ensures that the database can be restored to the most recent committed state after a restart and that transactions are either completely executed or completely undone.
The index server uses the preprocessor server for analyzing text data and extracting the information on which the text search capabilities are based.
The name server owns the information about the topology of SAP HANA system. In a distributed system, the name server knows where the components are running and which data is located on which server.
The statistics server collects information about status, performance and resource consumption from the other servers in the system.. The statistics server also provides a history of measurement data for further analysis.
Session and Transaction Manager
The Transaction manager coordinates database transactions, and keeps track of running and closed transactions. When a transaction is committed or rolled back, the transaction manager informs the involved storage engines about this event so they can execute necessary actions.
XS Engine is an optional component. Using XS Engine clients can connect to SAP HANA database to fetch data via HTTP.
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