8-Storage Structure

If rows are deleted in the block or if rows decrease

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Unformatted text preview: space within a block is managed for a data segment with PCTFREE=20 and PCTUSED=40 Block Space Usage Storage Structure Tathagata Bhattacharjee 3. If rows are deleted in the block or if rows decrease in size as a result of updates, block utilization may fall below 80%. However, a block is not used for inserts until the utilization falls below the PCTUSED, which in this example is 40% 4. When 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. Storage Structure DBA_TABLESPACES Tathagata Bhattacharjee DBA_DATA_FILES DBA_SEGMENTS Tablespaces Data Files DBA_FREE_SPACE DBA_EXTENTS Segments Free Extents Used Extents Data Dictionary Views Storage Structure Tathagata Bhattacharjee SQL> SELECT tablespace_name, count(*), max(blocks), sum(blocks) FROM dba_free_space GROUP BY tablespace_name SQL> SELECT extent_id, file_id, block_id, blocks FROM dba_extents WHERE owner = ‘scott’; SQL> SELECT segment_name, tablespace_name, extents, blocks FROPM dba_segments WHERE owner = ‘scott’; Obtaining Storage Information Storage Structure THANK YOU Tathagata Bhattacharjee...
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