Oracle8之前的rowid格式
bits 1 to 32 (bytes 1 to 4 ): block number inside the file containing the row (0-4294967295)
bits 33 to 48 (bytes 5 and 6): row number inside the block containing the row (0-65535)
bits 49 to 64 (bytes 7 and 8): file number (0-65535)
When printed, each byte was displayed by 2 hexadecimal characters (0-9A-F) and each field separated by a dot: BBBBBBBB.RRRR.FFFF
Oracle8开始之后的rowid格式，采用base64
bits 1 to 32 (bytes 1 to 4): data object id (0-4294967295)
bits 33 to 44 (byte 5 and half byte 6): file number inside the tablespace (0-4095)
bits 45 to 64 (half byte 6 and bytes 7 and 8): block number inside the file (0-1048575)
bits 65 to 80 (bytes 9 and 10): row number inside the block (0-65535)
When printed, each field is displayed in radix 64 (A-Za-z0-9+/): OOOOOOFFFBBBBBBRRR
Note that for a bigfile tablespace File and Block fields are combined to give Block number in the big file.bigfile tablespace的文件和块合并成块的编号，文件号是固定的1024.
AODU的rowid功能会把oracle8之后的格式转化为可读的格式，下面是样例
Note:oracle7的数据库很少有人用，所以没有做解析
AODU> rowid AAAAECAABAAAAgiAAA
Rowid Info
Data Object: 258 0x102
Rfile Number: 1 0x1
Block Number: 2082 0x822
Row Number: 0 0x0
AODU>
Reference
http://www.orafaq.com/wiki/ROWID
https://en.wikipedia.org/wiki/Base64
