---
title: Configuring a Client Application
---

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You can configure your native client application:

 - Programmatically in your app code
 - Via XML files and properties files (see [Client Cache XML Reference](../client-cache-ref.html))
 - Through a combination of programmatic and file-based approaches

This section describes configuration on two levels, the system level and the cache level.
System property settings describe your application's behavior, while cache configuration describes data.

## <a id="config_programmatic_vs_xml"></a>Programmatic Configuration vs XML Configuration

Programmatic configuration enables your client application to dynamically adapt to changing runtime conditions.

In contrast, XML configuration externalizes properties, such as locator addresses and pool
connection details, so they can be changed without requiring that you recompile your application.

**C++ RegionFactory Example**

The following examples illustrate how to set a region's expiration timeout attribute programmatically and through XML.

Setting a property programmatically:

``` cpp
    auto regionFactory = cache.createRegionFactory(RegionShortcut::CACHING_PROXY);
    auto region = regionFactory.setRegionTimeToLive(ExpirationAction::INVALIDATE,
                    std::chrono::seconds(120))
         .create("exampleRegion0");
```

XML equivalent:

``` xml
  <region name="exampleRegion0" refid="CACHING_PROXY">
    <region-attributes pool-name="default">
      <region-time-to-live>
        <expiration-attributes timeout="120s" action="invalidate"/>
      </region-time-to-live>
    </region-attributes>
  </region>
```

## Tables of properties

See [System Properties](sysprops.html) for a list of system properties that can be configured
programmatically or in the `geode.properties` file.

## <a id="config_high_availability"></a>High Availability with Server Redundancy

When redundancy is enabled, secondary servers maintain queue backups while the primary server pushes
events to the client. If the primary server fails, one of the secondary servers steps in as primary
to provide uninterrupted event messaging to the client. 
To configure high availability, set the `subscription-redundancy` in the client’s pool configuration. This setting indicates the number of secondary servers to use.
See the _<%=vars.product_name%> User Guide_ section [Configuring Highly Available Servers](<%=vars.serverman%>/developing/events/configuring_highly_available_servers.html)
for more details.