How does the data inserted after a delete command

Question

Hi Folks,
I have a question regarding a scenario. I deleted some data from a table ( i use the where clause to delete a portion of rows from the table). So after the rows are deleted the space is free but below the high water mark. When i insert new rows in the same table, then where from oracle fetches the space:
A. Will it use the space that is freed up by deleted the rows
B. Use the space above the high water mark. ( If it uses this space then Lets say all the extents are completed and we dont have any extents above the high water mark, then will it use the space freed by the deleted rows or will it complain for the addiditional space)
Please advice.
Also I would appriciate if you could give me a link for a documentation for the above scenerio.
Thanks in advance
Karthik

Answer 1

A. Will it use the space that is freed up by deleted
the rows That depends, it's controled by PCTUSED and PCTFREE parameter as described below. Also the free space need to be big enought to hold the new row.
The PCTUSED Parameter
The PCTUSED parameter sets the minimum percentage of a block that can be used for row data plus overhead before new rows are added to the block. After a data block is filled to the limit determined by PCTFREE, Oracle considers the block unavailable for the insertion of new rows until the percentage of that block falls beneath the parameter PCTUSED. Until this value is achieved, Oracle uses the free space of the data block only for updates to rows already contained in the data block.
B. Use the space above the high water mark. ( If it
uses this space then Lets say all the extents are
completed and we dont have any extents above the high
water mark, then will it use the space freed by the
deleted rows or will it complain for the addiditional
space)
When Extents Are Allocated
When you create a table, Oracle allocates to the table's data segment an initial extent of a specified number of data blocks. Although no rows have been inserted yet, the Oracle data blocks that correspond to the initial extent are reserved for that table's rows.
If the data blocks of a segment's initial extent become full and more space is required to hold new data, Oracle automatically allocates an incremental extent for that segment. An incremental extent is a subsequent extent of the same or greater size than the previously allocated extent in that segment.
Please advice.
Also I would appriciate if you could give me a link
for a documentation for the above scenerio.
check Oracle Concept for more detail,
Data Blocks, Extents, and Segments