It might be used right away, it might be used a few inserts later, it might never be reused.

It depends.


I'm going to assume bitmap managed free space here (ASSM - automatic segment space management). Here - when you go to insert, we need to find a block with sufficient free space. These blocks - the blocks allocated to your table under the high water mark - are managed on bitmap freelists. We'll walk through those in a semi hap-hazzard manner (we try to spread inserts out over many blocks to avoid concurrent insert concurrency issues). When we find a space to put it - we'll put it there. We don't go for a specific block, we go for a block with sufficient free space and that hopefully no one else is working on.

You might get lucky and reuse that block right away.

It might take a few inserts to get around to it.

If the table is very dynamic - lots of deletes + inserts - we might not get around to using it again - if ever. the table wouldn't grow or anything, we just might not need it.


We will tend to use that block however before we grab more blocks to put under the high water mark. So the table won't grow if there are free blocks under the high water mark.