Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 8 - RAC Administration

RAC Related Advantages 

An Oracle internal benchmark comparing the performance of automatic and manual segment space management, conducted on a two node Real Application Cluster database by inserting about 3 million rows in a table, showed that automatic segment space management provided a 35% performance gain over an optimally tuned segment (8 freelist groups, 20 freelists) using the manual mode.  (For more details, refer to Oracle MOSC Note 180608.1) 

Use the new dbms_space.space_usage procedure for reporting the space position in BMB segments. This procedure provides the space usage ratio within each block. It is preferred over the dbms_space.free_blocks procedure. Let us look at an example (a SQL Block) of how to get information about the blocks:

block_count.sql

DECLARE
 v_unformatted_blocks number;
 v_unformatted_bytes number;
 v_fs1_blocks number;
 v_fs1_bytes number;
 v_fs2_blocks number;
 v_fs2_bytes number;
 v_fs3_blocks number;
 v_fs3_bytes number;
 v_fs4_blocks number;
 v_fs4_bytes number;
 v_full_blocks number;
 v_full_bytes number;
BEGIN
dbms_space.space_usage ('SYSTEM', 'TEST', 'TABLE', v_unformatted_blocks,
v_unformatted_bytes, v_fs1_blocks, v_fs1_bytes, v_fs2_blocks, v_fs2_bytes,
v_fs3_blocks, v_fs3_bytes, v_fs4_blocks, v_fs4_bytes, v_full_blocks,
v_full_bytes);
dbms_output.put_line('Unformatted Blocks = '||v_unformatted_blocks);