rowid format and the format of a row piece

rowid format：

■ OOOOOO
The data object number identifies the segment (data object AAAPec in 
Example 12–1). A data object number is assigned to every database segment. 
Schema objects in the same segment, such as a table cluster, have the same data 
object number.
■ FFF
The tablespace-relative data file number identifies the data file that contains the 
row (file AAF in Example 12–1).
■ BBBBBB
The data block number identifies the block that contains the row (block AAAABS in 
Example 12–1). Block numbers are relative to their data file, not their tablespace. 
Thus, two rows with identical block numbers could reside in different data files of 
the same tablespace.
■ RRR
The row number identifies the row in the block (row AAA in Example 12–1). 
After a rowid is assigned to a row piece, the rowid can change in special 
circumstances. For example, if row movement is enabled, then the rowid can change 
because of partition key updates, Flashback Table operations, shrink table operations, 
and so on. If row movement is disabled, then a rowid can change if the row is exported 
and imported using Oracle Database utilities.

二、the format of a row piece