DBMS_SPACE.FREE_BLOCKS (    segment_owner     IN  VARCHAR2
                         ,  segment_name      IN  VARCHAR2
                         ,  segment_type      IN  VARCHAR2
                         ,  freelist_group_id IN  NUMBER
                         ,  free_blks         OUT NUMBER
                         ,  scan_limit        IN  NUMBER DEFAULT NULL
                         ,  partition_name    IN  VARCHAR2 DEFAULT NULL);  
Pragmas   pragma restrict_references(free_blocks,WNDS);  
segment_owner          - Schema name of the segment to be analyzed. 
segment_name           -  Segment name of the segment to be analyzed. 
segment_type           -  Type of the segment to be analyzed: TABLE, TABLE PARTITION, TABLE SUBPARTITION, INDEX, INDEX PARTITION, INDEX SUBPARTITION, CLUSTER, LOB 
freelist_group_id      -  Freelist group (instance) whose free list size is to be computed 
free_blks              -  Returns count of free blocks for the specified group 
scan_limit             -  Maximum number of free list blocks to read (optional). Use a scan limit of X you are interested only in the question, "Do I have X blocks on the free list?" 
partition_name         -  Partition name of the segment to be analyzed.      This is only used for partitioned tables; The name of subpartition should be used when partitioning is compose.