When
creating blocks, set the storage parameters to specify the way the data is
stored, how much space is to be used and to improve performance of the database
during transactions
PCTFREE and PCTUSED
These
parameters are used to set the space available to insert and update the blocks
PCTFREE
This
parameter is used to set the free space in a block that can be used for future
updates.
PCTUSED
PCTUSED
for a data segment represents the minimum percentage of used space that the
Oracle server tries to maintain for each data block of the table.
Some
points to remember when setting the values:
•The sum of PCTFREE and PCTUSED should not
be more than 100.
•Set a low PCTFREE and a high PCTUSED if
the table has many inserts and deletes and the updates do not increase the row
length.
•A high PCTFREE helps in reusing the free
space faster
•Set a low PCTFREE value if the table does
not have updates and row lengths are large.
•PCTFREE is set when creating tables,
cluster and indexes, but PCTUSED cannot be set when creating indexes.
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