METHOD 1:

CALCULATE THE BYTES OF A TABLE FOR EACH ROW.

SUPPOSE THE TABLE WILL HAVE ABOUT 1 LAC RECODS THEN,
TOTAL BYTES OF A ROW*100000 = THE ANSWER WILL BE IN BYTES
DIVIDE THE ANSWER/1024/1024 WHICH WILL BE IN MB

SO WE CAN GIVE THE INITIAL EXTENT OF THE TABLE FROM THE MB ARRIVED.

NEXT EXTENT =INITAIL EXTENT*1.25 WILL BE THE SIZE OF THE NEXT EXTENT OF THE TABLE.


METHOD 2:

CREATE A TABLE

ANALYZE TABLE EMP COMPUTE STATISTICS

SELECT NUM_ROWS,BLOCKS,EMPTY_BLOCKS,NUM_ROWS/BLOCKS FROM DBA_TABLES WHERE TABLE_NAME='EMP';

FROM THE QUERY YOU WILL GET THE NUMBER OF ROWS PER BLOCK SAY AROUND 25 ROWS PER BLOCK.

SO THAT MEANS HERE FOR 2048 BYTES THERE ARE ABOUT 25 ROWS.

FOR 1 LAC ROWS MEANS (100000*2048)/25 BYTES = 8192000

=> 8192000/1024/1024 = 8 MB(APPROX)


THIS WILL BE YOUR INITIAL EXTENT VALUE FOR THE TABLE.

FOR THE NEXT EXTENT SIZE INCREASCE THIS VALUE BY 25%.

HOPE THIS WILL HELP YOU.

THANKS,
SRIKANTH