Lecture 13 Storage Buffer

Lecture 13 Storage Buffer - Storage in Database Systems...

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1 Storage in Database Systems CMPSCI 445 Fall 2012
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Storage Topics v Architecture and Overview v Disks v Buffer management v Files of records 2
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3 DBMS Architecture Disk Space Manager Buffer Manager Query Parser Query Rewriter Query Optimizer Query Executor Lock Manager Log Manager
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4 Data on External Storage v Disks: Can retrieve random page at fixed cost § But reading several consecutive pages is much cheaper than reading them in random order v Tapes: Can only read pages in sequence § Cheaper than disks; used for archival storage v Page: Unit of information read from or written to disk § Size of page: DBMS parameter, 4KB, 8KB v Disk space manager: § Abstraction: a collection of pages. § Allocate/de-allocate a page. § Read/write a page. v Page I/O : § Pages read from disk and pages written to disk § Dominant cost of database operations
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5 Buffer Management v Architecture: § Data is read into memory for processing § Data is written to disk for persistent storage v Buffer manager stages pages between external storage and main memory buffer pool. v Access method layer makes calls to the buffer manager.
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6 Access Methods v Access methods: routines to manage various disk-based data structures. § Files of records § Various kinds of indexes v File of records: § Important abstraction of external storage in a DBMS! § Record id (rid) is sufficient to physically locate a record v Indexes : § Auxiliary data structures § Given values in index search key fields, find the record ids of records with those values
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Lecture 13 Storage Buffer - Storage in Database Systems...

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