When you are using Ehcache as the cache manager in some Interact environments, a high number of concurrent sessions may cause the Interact runtime to exceed its available memory, causing a system slowdown or out-of-memory error. An out-of-memory situation is more likely if you have increased the maxEntriesInCache configuration parameter (Interact > cacheManagement > Caches > InteractCache > maxEntriesInCache) to a number higher than the default setting, although it can occur even with the default setting of a maximum of 100,000 sessions. To avoid this issue, you can reduce the maxEntriesInCache value, or you can follow the instructions here to modify the system memory cache to roll the cached memory over to disk storage. This modification allows many more concurrent sessions than would otherwise be possible.

<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:noNamespaceSchemaLocation="../../main/config/ehcache.xsd"> 

<defaultCache
maxElementsInMemory="10"
eternal="false"
timeToIdleSeconds="5"
timeToLiveSeconds="10"
overflowToDisk="true"
/>

<cache name="InteractCache"
maxElementsInMemory="5"
eternal="false"
timeToIdleSeconds="600"
timeToLiveSeconds="600"
overflowToDisk="true">

<cacheEventListenerFactory 
class="com.unicacorp.interact.cache.ehcache.EHCacheEventListenerFactory"
 properties=""/>
<!--For InteractCache, use the following to use the 
EHCacheEventListenerFactory:-->
<cacheEventListenerFactory 
class="com.unicacorp.interact.cache.EHCacheEventListenerFactory"
 properties=""/>
<!--For PatternStateCache, use the following to use 
the EHCacheEventListenerFactory:-->
<cacheEventListenerFactory 
class="com.unicacorp.interact.cache.PatternStateCacheEventListenerFactory"
 properties=""/>
</cache>

</ehcache>