Q10: Briefly describe how space within a block is managed for a data segment with PCTFREE = 20 and PCTUSED = 40?
The following steps explain how space within a block is managed for a data segment with PCTFREE = 20 and PCTUSED = 40:1Rows re inserted into the block until the free space in the block is equal or less than 20%. The block is no longer available for inserts when rows occupy 80%(100 – PCTFREE) or more of the available data space in the block.2The remaining 20% can be used when the size of a row increases. For example, a column that was originally NULL is updated to be assigned a value. Thus block utilization may be in excess of 80% as a result of updates.3If rows are deleted in the block or if rows decrease in size as a result of updates, blockutilization may fall below 80%. However, a block is not used for inserts until the utilization falls below PCTUSED, which in this example is 40%.4When the utilization falls below PCTUSED, the block is available for inserts. As rows are inserted into the block, the utilization of the block increases and the cycle repeats starting with step 1.
You've reached the end of your free preview.
Want to read all 5 pages?
Oracle Database, Oracle Corporation, Disk partitioning