关于undo slot的解释

今天在网上给一个puber的undo slot的解释如下：

A transaction begins when a slot is allocated in the transaction table at the head of a rollback segment. This is the
B]i-y-kDQ&H0physical manifestation of a transaction. The transaction identifier (Txid) is a pointer to this location.
i} v0? wn0The transaction identifiers(Txid) have the following structure:
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w Y#_Fd.XYL0txid=usn.slot.wrap  (undo_segment_number.transaction_slot_id.scn wrap).
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也可以形象地理解成：ITPUB个人空间:Bb dA nOp'U

Fr%tI'WnN0该事务所占用的回滚段号与该事务在该回滚段的事务表（Transaction table）中所占用的槽号（slot number，可理解为记录号）。
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