In 6.2 we added a cap for field size to limit the risk of unbounded memory growth. This field is MaxFieldSize, but unfortunately it didn't make it the docs.
http://docs.splunk.com/Documentation/StreamApp/6.2.2/DeployStreamApp/ConfigureStreamForwarder#Configure_streamfwd.xml
That docs page covers how to configure streamfwd.xml, and if you add a MaxFieldSize parameter you can up the limit to something larger if you're concerned about RAM growth or if not you can set the value to 0 for unlimited.
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