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Oracle10g Grid Computing with RAC
Chapter 17 - Oracle’s Grid Integration Technologies

Bigfile Tablespace Benefits

Rowids of Rows that belong to BFTs do not contain the relative file number.

• Smallfile tablespace has a four-pieces format, OOOOOOFFFBBBBBBRRR, in which:
   

• OOOOOO is the data object number of the segment.
   

• FFF is the tablespace-relative datafile number of the datafile that contains the row.
   

• BBBBBB is the data block that contains the row.
   

• RRR is the slot number identifying the row inside a particular block.

Bigfile Tablespace Rowid Format

In a bigfile tablespace, there is only one file that always has a relative file number of 1024.  A bigfile tablespace has a three-piece format, OOOOOOLLLLLLLLLRRR, in which LLLLLLLLL is used to denote the block number.  The concatenation of FFF and BBBBBB makes the encoded block number.

For BFTs, the only supported way of getting components of extended rowids is to use the DBMS_ROWID package.

Here is an example on how to use the dbms_rowid package to retrieve rowid information:

select dbms_rowid.rowid_relative_fno(rowid, 'BIGFILE') 
       bigfile_rowid,
       dbms_rowid.rowid_relative_fno(rowid, 'SMALLFILE')
       smallfile_rowid,
       first_name, last_name
FROM   hr.employees where  rownum < 3;

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