protected boolean isUpdate() {
    // This event can be in one of three states:
    // - in memory primary (initialized)
    // - in memory secondary (not initialized)
    // - evicted to disk, read back in (initialized)
    // In the first case, both the operation and action are set.
    // In the second case, only the operation is set.
    // In the third case, only the action is set.
    return operation == null ? action == UPDATE_ACTION
        : operation == EnumListenerEvent.AFTER_UPDATE;
  }
Returns whether this <code>GatewayEvent</code> represents an update.

@return whether this <code>GatewayEvent</code> represents an update
geode-core/src/main/java/org/apache/geode/internal/cache/wan/GatewaySenderEventImpl.java