WebSphere eXtreme Scale Primer, part-3 : concepts

  • Key – A Java object instance that identifies a single cache value
  • Value – A Java object instance that contains the cache data
  • Map – An interface that stores data as key-value pairs
  • MapSet – A collection of maps whose entries are logically related
  • Grid – A collection of map sets
  • Partition – The concept of splitting data into smaller sections
  • Shard – The data in a partition is physically stored in shards.
  • Grid Container – Grid containers host shards
  • Grid Container Server – A grid container server hosts grid containers
  • Catalogue Server – A catalogue server controls grid container servers.



A grid container server can host many grid containers.
A grid container hosts shards, which can be from one or more grids.
A grid can be spread across many grid containers.
The catalog service places shards in grid containers.
A grid consists of a number of map sets. A map set is partitioned using a key. Each map in the map set is defined by a BackingMap.
A map set is a collection of maps that are typically used together. Many map sets can exist in one grid.
A map holds (grid) data as key value pairs.
A map set consists of a number of partitions. Each partition has a primary shard and N replica shards.