CS411 - Transaction Management - Note 1 - 2

Buffer data indexes log etc lock tables main memory

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Unformatted text preview: to make sure it interleave with a way that if it goes wrong, we can still rollback. When the system declares that the transaction to disk is successful, we want to make sure that even the disk fails, the result is still permanent and it still work. Be careful with this kind of things! We want to make a reliable system. Slight error can make a system completely unusable. Therefore we have to make a system failure tolerant as much as possible. Financial system can be some examples of higher failure tolerant system. Example: Banking records cannot lose their data, which is very important! Correctness of Transactions (5 of 12) Transaction Management (16 of 61) Think about it like component for controlling processes in operation systems: Transaction Manager (or TP Monitor) • Part of the DBMS • Main duties: o Start transactions o Logs transactions o Detects/avoid issues o Executes recovery processes • Starts transactions • locate and start the right program • ensure timely, fair scheduling • Logs their activities • especially start/stop, writes, commits, aborts • Detects or avoids conflicts • Takes recovery actions Correctness of Transactions (6 of 12) Transaction Management (17 of 61) Diagram of a typical DBMS architecture. DBMS Architecture User/Web Forms/Applications/DBA query transaction DDL commands Query Parser Transaction Manager DDL Processor Concurrency Control Logging & Recovery Query Rewriter Query Optimizer Query Executor Records Indexes Buffer Manager Storage Manager Storage Correctness of Transactions (7 of 12) DBMS will handle this, and so as a programmer we have to write a program correct to avoid problems. Buffer: data, indexes, log, etc Lock Tables Main Memory Question: What else is happening besides the query? First part of DBMS architecture is the query part, and it is about querying and fetching the requested data. Transaction part is in the middle, and it handles logging and concurrency issues. data, metadata, indexes, log, etc Transaction Management (18 of 61) DBMS is like an operating system in that it needs its way to handle virtual memory. DBMS needs buffer memory for its specific work so that reliability and recovery is ensured, independent from OS virtual memory. Logging keeps tracks of executions and is cruc...
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