+ * The possible persistence options. This specify whether (and for how long) the
+ * node remembers to execute a request and the results. Possible values are
+ * <code>connection</code>, <code>reboot</code>, and <code>forever</code>.
+ * <code>connection</code> means that a request is aborted as soon as the
+ * connection to the node is severed. <code>reboot</code> means that a request
+ * is remembered as long as the node is running but not after restarts.
+ * <code>forever</code> finally means that a request persists until it is
+ * explicitely deleted.
+ *