geode-docs/developing/distributed_regions/region_entry_versions.html.md.erb

---
title: Consistency for Region Updates
---

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<a id="topic_CF2798D3E12647F182C2CEC4A46E2045"></a>


<%=vars.product_name%> ensures that all copies of a region eventually reach a consistent state on all members and clients that host the region, including <%=vars.product_name%> members that distribute region events.

-   **[Consistency Checking by Region Type](how_region_versioning_works.html#topic_7A4B6C6169BD4B1ABD356294F744D236)**

    <%=vars.product_name%> performs different consistency checks depending on the type of region you have configured.

-   **[Configuring Consistency Checking](how_region_versioning_works.html#topic_B64891585E7F4358A633C792F10FA23E)**

    <%=vars.product_name%> enables consistency checking by default. You cannot disable consistency checking for persistent regions. For all other regions, you can explicitly enable or disable consistency checking by setting the `concurrency-checks-enabled` region attribute in `cache.xml` to "true" or "false."

-   **[Overhead for Consistency Checks](how_region_versioning_works.html#topic_0BDACA590B2C4974AC9C450397FE70B2)**

    Consistency checking requires additional overhead for storing and distributing version and timestamp information, as well as for maintaining destroyed entries for a period of time to meet consistency requirements.

-   **[How Consistency Checking Works for Replicated Regions](how_region_versioning_works.html#topic_C5B74CCDD909403C815639339AA03758)**

    Each region stores version and timestamp information for use in conflict detection. <%=vars.product_name%> members use the recorded information to detect and resolve conflicts consistently before applying a distributed update.

-   **[How Destroy and Clear Operations Are Resolved](how_region_versioning_works.html#topic_321B05044B6641FCAEFABBF5066BD399)**

    When consistency checking is enabled for a region, a <%=vars.product_name%> member does not immediately remove an entry from the region when an application destroys the entry. Instead, the member retains the entry with its current version stamp for a period of time in order to detect possible conflicts with operations that have occurred. The retained entry is referred to as a *tombstone*. <%=vars.product_name%> retains tombstones for partitioned regions and non-replicated regions as well as for replicated regions, in order to provide consistency.

-   **[Transactions with Consistent Regions](how_region_versioning_works.html#topic_32ACFA5542C74F3583ECD30467F352B0)**

    A transaction that modifies a region having consistency checking enabled generates all necessary version information for region updates when the transaction commits.