Fragmenting the index in the same way as the table

You fragment an index in the same way that you fragment the table when you create a fragmented table and subsequently create an index without specifying a fragmentation strategy, unless the distribution scheme is round-robin and automatic location is enabled. Indexes on tables that use the round-robin distribution scheme are not fragmented when the AUTOLOCATE configuration parameter or environment option is set to a positive integer.

For example, suppose you create a fragmented table and index with the following SQL statements: 
CREATE TABLE tb1(a int) 
   FRAGMENT BY EXPRESSION
      (a >=0 AND a < 5) IN db1,
      (a >=5 AND a <10) IN db2,
      (a >=10 AND a <15) IN db3;
CREATE INDEX idx1 ON tb1(a);

The database server fragments the index keys into dbspaces db1, db2, and db3 with the same column a value ranges as the table because the CREATE INDEX statement does not specify a fragmentation strategy.

Suppose you then decide to detach the data in the third fragment with the following SQL statement: 
ALTER FRAGMENT ON TABLE tb1 
   DETACH db3 tb3;

Because the fragmentation strategy of the index is the same as the table, the ALTER FRAGMENT DETACH statement does not rebuild the index after the detach operation. The database server drops the fragment of the index in dbspace db3, updates the system catalog tables, and eliminates the index build.