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【正文】 Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Data Dictionary Storage 數(shù)據(jù)字典存儲(chǔ) ? Information about relations ? names , 屬性名，類(lèi)型，長(zhǎng)度 ， views， ? integrity constraints ? 用戶賬號(hào)，口令 ? 關(guān)于 DB 本身的統(tǒng)計(jì)數(shù)據(jù) ? 物理組織 Physical file anization information ? 物理存儲(chǔ) (sequential/hash/…) ? Physical location of relation ， DISK ,Block ? Information about indices 索引 (Chapter 12) Data dictionary 或 system catalog stores metadata: data about data, such as : 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Sequential File Organization ? 適用于 處理 序列性，歷史性 數(shù)據(jù)的場(chǎng)合 ? 按某個(gè)或幾個(gè)屬性 排序 searchkey 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. VariableLength Records: Slotted Page Structure 變長(zhǎng)記錄 槽口 存頁(yè)面結(jié)構(gòu) ? Slotted page header contains: 文件頭存 : ? number of record entries 記錄個(gè)數(shù) ? end of free space in the block 回收列表結(jié)束 ? location and size of each record每個(gè)記錄起止 ? 與 光盤(pán)目錄的組織 有點(diǎn)相似 169。 will consider variable length records later. 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Buffer Manager ? Programs call on the buffer manager when they need a block from disk. 1. If the block is already in the buffer, buffer manager returns the address of the block in main memory 2. If the block is not in the buffer, the buffer manager 1. Allocates space in the buffer for the block 1. Replacing (throwing out) some other block, if required, to make space for the new block. 2. Replaced block written back to disk only if it was modified since the most recent time that it was written to/fetched from the disk. 2. Reads the block from the disk to the buffer, and returns the address of the block in main memory to requester. 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Storage Hierarchy ?各層 ?存儲(chǔ)速度有數(shù)量級(jí)的差別 ?至少 10倍 慢介質(zhì)以廉價(jià)和容量而頑固地不肯退出歷史舞臺(tái) 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(xiě) ? 有限次讀寫(xiě) 目前質(zhì)量： 110萬(wàn)次，夠用了 ? Reads are roughly as fast as main memory 讀快 ? 寫(xiě)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。 volatile。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Chapter 11: Storage and
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