SM_SNMP_MAX_MESSAGE_SIZE is an environment variable that controls the maximum size of the SNMP datagram that is processed. The default value is 8k (8192 bytes).
The default size can be overridden by setting the environment variable SM_SNMP_MAX_MESSAGE_SIZE to the required maximum size. For example, setting SM_SNMP_MAX_MESSAGE_SIZE equal to 16384 sets the maximum to 16k, which is double the default value.
If you try to set SM_SNMP_MAX_MESSAGE_SIZE to less than 1472 (the recommended minimum for UDP/IPv4 per RFC-3417, section 3.2), it will be silently adjusted to be exactly 1472.
Although SM_SNMP_MAX_MESSAGE_SIZE can be used to set the maximum SNMP datagram size to less than the default 8k, this is strongly discouraged.
If you try to set SM_SNMP_MAX_MESSAGE_SIZE greater than 64k (65536 bytes), it will be set to exactly 65536. A value of 65536 bytes is the largest possible datagram size supported by UDP.
Setting SM_SNMP_MAX_MESSAGE_SIZE to large values will increase server memory usage. This is especially true for trap processing during periods of high trap reception rate. Therefore, this option should only be used when it is needed to communicate with SNMP devices sending unusually large datagrams. Only increase the setting of this environment variable on the specific Domain Managers which manage those devices.