Database Reference
In-Depth Information
If we compare the space utilization of the two tables after that operation, as follows, we can see that as we load
more and more data into the table
UNIFORM_TEST
using parallel direct path operations, the space utilization gets worse
over time:
EODA@ORA12CR1> exec show_space( 'UNIFORM_TEST' );
Unformatted Blocks ..................... 0
FS1 Blocks (0-25) ...................... 0
FS2 Blocks (25-50) ..................... 0
FS3 Blocks (50-75) ..................... 0
FS4 Blocks (75-100)..................... 25,564
Full Blocks ............................ 306,152
Total Blocks............................ 332,800
Total Bytes............................. 2,726,297,600
Total MBytes............................ 2,600
Unused Blocks........................... 0
Unused Bytes............................ 0
Last Used Ext FileId.................... 5
Last Used Ext BlockId................... 320,128
Last Used Block......................... 12,800
PL/SQL procedure successfully completed.
EODA@ORA12CR1> exec show_space( 'AUTOALLOCATE_TEST' );
Unformatted Blocks ..................... 0
FS1 Blocks (0-25) ...................... 0
FS2 Blocks (25-50) ..................... 0
FS3 Blocks (50-75) ..................... 0
FS4 Blocks (75-100)..................... 0
Full Blocks ............................ 306,152
Total Blocks............................ 307,392
Total Bytes............................. 2,518,155,264
Total MBytes............................ 2,401
Unused Blocks........................... 0
Unused Bytes............................ 0
Last Used Ext FileId.................... 6
Last Used Ext BlockId................... 301,312
Last Used Block......................... 6,240
PL/SQL procedure successfully completed.
We would want to use a significantly smaller uniform extent size or use the
AUTOALLOCATE
clause. The
AUTOALLOCATE
clause may well generate more extents over time, but the space utilization is superior due to the extent
trimming that takes place.
■
i noted earlier in this chapter that your mileage may vary when executing the prior parallelism examples. it's
worth highlighting this point again; your results will vary depending on the version of oracle, the degree of parallelism
used, and the amount of data loaded. the prior output in this section was generated using oracle 12
c
release 1 with the
default degree of parallelism on a 4 Cpu box.
Note
