GMSST (1-byte character string)
Flag indicating whether message retrieved is a segment of a logical message.
It has one of the following values:
- SSNSEG
- Message is not a segment.
- SSSEG
- Message is a segment, but is not the last segment of the logical message.
- SSLSEG
- Message is the last segment of the logical message.
This is also the value returned if the logical message consists of only one segment.
This is an output field. The initial value of this field is SSNSEG. This field is ignored if GMVER is less than GMVER2.