You cannot force oracle coalesce free space inside block

404 Part III ✦ Administering Storage for Oracle Objects

Block space utilization parameters must be specified in the STORAGE clause of a segment and cannot be specified in the DEFAULT STORAGE clause of a tablespace.

This is because each table or index has different characteristics and, unless your tablespace contains only one table or index, it does not make sense to have the same settings for all segments on the tablespace. You should determine the optimal setting of these parameters before creating the segment.

Chapter 9 ✦ Storage Structure and Relationships 405

However, if you wanted to ensure that no more than a specific number of transac-tion slots were ever allocated on a block, you can specify a value other than the default. For example, setting MAXTRANS to 10 would not allow any more than ten transactions to modify data on the block. If more than ten transactions are needed to modify data on the block, the eleventh would need to wait until one of the other transactions completed. Similarly, if there were not sufficient free space in the block to allocate additional transaction slots, any subsequent transaction would also need for a previous one to finish before it could go ahead. For these reasons, as well as to deal with variable character columns, it is important that sufficient free space remains on the block.

PCTFREE