In that case, setting DB_FILE_
MULTIBLOCK_READ_COUNT to a value higher than 16 will not affect the performance of the
full table scans.
Estimating Space Requirements for Tables
As of Oracle Database 10g, you can use the CREATE_TABLE_COST procedure of the DBMS_
SPACE package to estimate the space required by a table. The procedure determines the space
required for a table based on attributes such as the tablespace storage parameters, the tablespace
block size, the number of rows, and the average row length. The procedure is valid for both
dictionary-managed and locally managed tablespaces.
TIP
When you create a new table using Oracle Enterprise Manager DB
Control, you can click the Estimate Table Size button to estimate table
size for a given estimated row count.
There are two versions of the CREATE_TABLE_COST procedure (it is overloaded so you can
use the same procedure both ways). The first version has four input variables: tablespace_name,
avg_row_size, row_count, and pct_free. Its output variables are used_bytes and alloc_bytes.
The second version??™s input variables are tablespace_name, colinfos, row_count, and pct_free;
its output variables are used_bytes and alloc_bytes. Descriptions of the variables are provided
in the following table:
Parameter Description
tablespace_name The tablespace in which the object will be created.
avg_row_size The average length of a row in the table.
colinfos The description of the columns.
Pages:
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268