Why we must not use read/write static fields.
But using read-only (final) static fields is allowed.
Because you are not allowed to implement your own synchronisation within EJBs.
If you trying to emulate a static counter, then good luck :)
One nasty work around is to have a BMP entity bean which actually doesn't do any persistence.
EJBs were designed to be distributed, making static synchronisation impossible (unless you come up with a way to have multiple servers running the same JVM! ).