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WBM_MSG_LOWER is one of three system parameters available for managing the update traffic between a master write bitmap and its corresponding local write bitmaps in an OpenVMS Cluster system. The others are WBM_MSG_INT and WBM_MSG_ UPPER. These parameters set the interval at which the frequency of sending messages is tested and also set an upper and lower threshold that determine whether the messages are grouped into one SCS message or are sent one by one. WBM_MSG_LOWER is the lower threshold for the number of messages sent during the test interval that initiates single-message mode. In single-message mode, the writes issued by each remote node are, by default, sent one by one in individual SCS messages to the node with the master write bitmap. If the writes sent by a remote node reach an upper threshhold of messages during a specified interval, single-message mode switches to buffered- message mode. The minimum value of WBM_MSG_LOWER is 0 messages per interval. The maximum value is -1, which corresponds to the maximum positive value that a longword can represent. The default is 10. WBM_MSG_LOWER is a DYNAMIC parameter.