Designing a Distribution Scheme

After you decide whether to fragment table rows, index keys, or both, and you decide how the rows or keys should be distributed over fragments, you decide on a scheme to implement this distribution.

The database server supports the following distribution schemes:

• Round-robin. This type of fragmentation places rows one after another in fragments, rotating through the series of fragments to distribute the rows evenly.

  For smart large objects, you can specify multiple sbspaces in the PUT clause of the CREATE TABLE or ALTER TABLE statement to distribute smart large objects in a round-robin distribution scheme so that the number of smart large objects in each space is approximately equal.

  For INSERT statements, the database server uses a hash function on a random number to determine the fragment in which to place the row. For INSERT cursors, the database server places the first row in a random fragment, the second in the next fragment sequentially, and so on. If one of the fragments is full, it is skipped.

• Expression-based. This type of fragmentation puts rows that contain specified values in the same fragment. You specify a fragmentation expression that defines criteria for assigning a set of rows to each fragment, either as a range rule or some arbitrary rule. You can specify a remainder fragment that holds all rows that do not match the criteria for any other fragment, although a remainder fragment reduces the efficiency of the expression-based distribution scheme.