= Updates included in Chronicle Map 3
Neil Clifford
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Changes between Chronicle Map 3 and the previous Chronicle Map version are detailed below:

== Functional changes

 - Chronicle Map 3 has a https://github.com/OpenHFT/Chronicle-Map/blob/doco_refresh/spec[formal data store specification] that specifies the https://github.com/OpenHFT/Chronicle-Map/blob/doco_refresh/spec/1-design-goals.md#guarantees-1[guarantees] that the data store provides, and gives a way to verify those guarantees.

 - Added support for multi-key queries.

 - "Listeners" mechanism fully reworked; see <<CM_Tutorial_Behaviour.adoc#,Behaviour Customization>>. This has a number of important consequences, most notable is that it is now possible to define "eventual-consistency" replication strategy, different from "last write wins"; any state-based CRDT.

 - "Stateless clients" functionality (remote calls) is moved to Chronicle Datagrid.

 - Replication is performed using Chronicle Datagrid.

 - Earlier versions of Chronicle Map had hard creation-time limits on the number of entries storable in a Chronicle Map. If the size exceeded this limit, an exception was thrown. +
 In Chronicle Map 3, this limitation is removed. The number of entries still has to be configured when the Chronicle Map is created, Exceeding this configured limit is possible, but discouraged. +
 For more information, see <<CM_Tutorial.adoc#configure-entries,Configure entries>>.

 - Chronicle Map 3 supports <<CM_Tutorial.adoc#entry-checksums,entry checksums>> that enables detection of  data corruption, providing additional safety.

 - Chronicle Map 3 allows <<CM_Tutorial.adoc#recovery,recovery>> after failures and corruptions.

 - Minor improvements and fixes.

== Non-functional changes

 - Chronicle Map 3 requires Java version 8, or later.

 - Chronicle Map 3 has <<CM_Compatibility_and_Versioning.adoc#,versioning and compatibility policies>>.

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