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Dictionary Cache Locks (361)

原创 IT综合 作者:tsinglee 时间:2007-12-13 10:26:55 0 删除 编辑

These locks are of very short duration and are held on entries in
dictionary caches while the entries are being modified or used. They guarantee that
statements being parsed do not see inconsistent object definitions.

Dictionary cache locks can be shared or exclusive. Shared locks are released when the
parse is complete. Exclusive locks are released when the DDL operation is complete.

字典缓存锁
1. 当用户更新或使用时数据字典缓存内的条目时,需要获取条目上的字典缓存锁.
保证被解析的语句不会看到不一致的对象定义
2. 字典缓存锁分为共享和排他两类 . 共享锁在解析完成后结束, 排他锁则在DDL操作结束后释放

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