extent allocation?

When Oracle requests an extent of block size 210, does it require this extent to be in contiguous memory? Got the following error on one of my sql query that union few tables:

  ORA-01547: failed to allocate extent of size 210 in tablespace 'SYSTEM'

Looked into the dba_free_space and saw many blocks of smaller sizes. Is there a way to tell Oracle to use multiple extents for the query? Also, is there a quick way to consolidate the memory without backup of the database?

Thanks!

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Un Un Fu                                    Internet: un_at_gdstech.grumman.com
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