chapter11storageandfilestructure(存儲(chǔ)版)
【正文】 darshan Database System Concepts 5th Edition, Oct 23, 2022. Clustering File Organization 聚簇文件 ? 不同型但相關(guān)的數(shù)據(jù)放在一起 （舊式大家庭： 幾代同堂 ） ? ., clustering anization of customer and depositor: ? 作這兩各關(guān)系連接時(shí)，快 ? results in variable size records 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Sequential File Organization (Cont.) ? 刪除 – use pointer chains ? 插入 – 有縫插針 ，無(wú)縫 鏈溢 overflow block，更新指針 ? 與時(shí)俱進(jìn) 重排序 reanize time to time to restore sequential order 無(wú)縫鏈溢 （ 溢出塊） 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. FixedLength Records ? Simple approach: ? Store record i starting from byte n ? (i – 1), where n is the size of each record. ? Record access is simple but records may cross blocks ? Modification: do not allow records to cross block boundaries ? Deletion of record i: alternatives: ? move records i + 1, . . ., n to i, . . . , n – 1 ? move record n to i ? do not move records, but link all free records on a free list 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Storage Hierarchy (Cont.) 存儲(chǔ)分級(jí) ? primary storage: 主存 ，快 ，易逝 ? secondary storage: next level in hierarchy, nonvolatile, moderately fast access time ? also called online storage ? . flash memory, magic disks 閃存，磁盤 ? tertiary storage: lowest level in hierarchy, nonvolatile, slow access time 第 3存儲(chǔ) ? also called offline storage ? . magic tape, optical storage 磁帶光盤 169。 managed by the puter system hardware. 快， 易逝， 硬件 ?高速高價(jià) ?設(shè)備 ?低速低價(jià) ?設(shè)備 ?多種 Cache： ?CPU與內(nèi)存 ?內(nèi)存與磁盤 ?OS與 DBMS 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Chapter 11: Storage and File Structure ? Overview of Physical Storage Media ? Storage Access ? File Organization ? Organization of Records in Files ? DataDictionary Storage 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Physical Storage Media (Cont.) ? Flash memory 閃存 ? Data survives power failure 非易逝 ? Data can be written at a location only once, but location can be erased and written to again 可重寫 ? 有限次讀寫 目前質(zhì)量： 110萬(wàn)次，夠用了 ? Reads are roughly as fast as main memory 讀快 ? 寫稍微慢 ? 貴 ， ? 用于嵌入式設(shè)備 ， 數(shù)字相機(jī) MP3 ? also known as EEPROM (Electrically Erasable Programmable ReadOnly Memory) 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Buffer Manager ? Programs call on the buffer manager when they ne
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