Looking at the error you're getting doesn't look like that has anything to do with the 4k limitation on the blob data type in MySQL or JBCACHE-320. In the blob case you'd get NPE upon truncation of the data stored. I think the problem has to do with the serialization of the objects that you're persisting. the failure doesn't happen in MySQL but rather on deserialization. Please review your object serialization / deserialization mechanism and if you're sure that it's working correctly then please turn up JBC logging level to debug and post the log part that pertain to the database retrieve so I can examine it further. Cheers, Hany View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4117951#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...