Oracle Extended Rowid Format
Oracle Tips by Burleson Consulting

As an alternative to DBMS_ROWID, one could just decode the ROWID from the query based on what is known as the Extended Rowid Format Oracle uses. The base-64 decomposition of 'AAAMfMAAEAAAAAgAAH' works out to be the following.:

 

Data Object ID	Relative File No	Block Number	Row Slot(Number)
AAAMfM	AAE	AAAAAg	AAH
51148	4	32	7

 

Oracle uses a conversion table of A-Z being 0-25 in decimal form, and a-z being 26-51. Once one has the decimal value, one can derive the binary value and then string the binary strings together to get the final value. For example, the M and f components under the data object ID are decimal values 12 and 31 whose binary values are 001100 and 011111. AAAMfM is then represented as:

 

000000 000000 000000 001100 011111 001100

 

The decimal value of this is then computed to be 51148 and matches what was shown earlier. Of course, the DBA could also just query DBA_OBJECTS to get the DATA_OBJECT_ID value of the table.

 

Two other preliminary items need to be mentioned at this point. The first concerns setting up a UNIX environment. If one has the resources at work, where resources implies a totally throw-away database on a totally throw-away ORACLE_HOME installation on a server that can be down in case one has to reinstall Oracle, there is already one made. All the DBA needs to do is make the executable if not already done.

 

If the DBA does not have a UNIX server, how does he get access to one, i.e. the DBA is doing this on a home computer? One option is to buy a bare bones PC and install Oracle Enterprise Linux on it. Another is to install OEL on the current PC and live with booting from multiple operating systems. The boot from multiple systems on the main home PC is not the best choice, but one can make that happen with relatively little effort. If one does not like having OEL or some other brand of Linux on the PC, it can be removed later and the disk space it partitioned can be reclaimed.

 

The second is using a parameter file when starting bbed. Nothing new about what a parameter file is and does as it is just like parameter files used elsewhere in Oracle (exp, imp, sqlldr, etc.). What is new, however, are the parameters and their values or options. Enter bbed help=y to see the list. In this example, bbed is located in $ORACLE_HOME/bin after having been compiled elsewhere.

 

Collect the file name information as shown earlier. Identify the block size of the file(s), and for the initial runs of using this tool, use the browse mode. The contents of a parameter file are shown below.