Partitions: semantic and round-robin strategies

This functionality is available in Adaptive Server 15.0 and later.

Partitioning can help manage large tables and indexes by dividing them into smaller, more manageable pieces; partitioning can provide faster and easier access to data.

Each partition can reside on a separate segment. Partitions are database objects with unique IDs and can be managed independently. You can, for example, load data and create indexes at the partition level. Yet partitions are transparent to the end user.

Adaptive Server supports horizontal partitioning, in which a selection of table rows can be distributed among storage devices. Individual table or index rows are assigned to a partition according to a partitioning strategy. By default, Adaptive Server creates every table and index with a single, round-robin partition. You can also choose a semantics-based strategy that assigns rows to partitions:

Using a system-generated hashing function (hash partitioning), or
According to whether one or more values in a row falls within a range of predefined values for the partition (range partitioning), or
According to whether one value in the row matches one of a set of predefined values unique for each partition (list partitioning).

Semantics-based partitioning is a separately licensed feature. To enable semantic partitioning at a licensed site, set the value of the enable semantic partitioning configuration parameter to 1. You can configure Adaptive Server parameters from the server property sheet or by right-clicking the server icon and selecting Configure from the dropdown menu.

A data partition is a subset of a table, and shares the column definitions and referential and integrity constraints of the base table.

Every partitioned table has one or more partitioning columns. The values in these columns, called partitioning keys, determine the partition assignment for each row.

You can specify partitioning columns of any type except:

text and image
bit
Java classes
Computed columns

An index partition is an independent database object with a unique partition ID; it is a subset of an index, and resides on a segment or other storage device.

You can mix multipartitioned and single-partitioned (default) indexes with multipartitioned tables:

A multipartitioned table can have multipartitioned and single-partitioned indexes.
A single-partitioned table can have only single-partitioned indexes.

Adaptive Server supports multipartitioned local indexes and single-partitioned global indexes. A local index is always equipartitioned with its base table; that is, the table and index share the same partitioning keys and partitioning criteria. A local index partition spans only one data partition.