objd, dba, slot

今天问了一个非常愚蠢的问题，自己学习Oracle已经快2年多了，既然还问人家：
    objd, dba, slot是什么？干什么用的？

说明自己没有真正的明白。 写上，找到后给补详细些。

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objd:
    Is assigned to each data object, such as table or index when it is created, and it is unique within the database.

objd:
    刚开始的时候表的objn和objd是一样，每次truncate table后objd的值将会逐渐增加。视图的objd值为0。

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data block address (DBA)：

The DBA (here: not the database administrator but the data block address) uniquely identifies a database block in the database.
Behind such a database block address is a datafile number and the block number within that database file.
The datafile number can be found with dbms_utility.data_block_address_file. The block number within this file can be found with dbms_utility.data_block_address_block. A database block address can be constructed from a datafile number and a block number with make_data_block_address.

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slot：
    DBMS_ROWID can be used to convert ROWIDs into a
        File id (rowid_relative_fno)
        Block number (rowid_block_number)
        Slot number in block (rowid_row_number)