Details

Actual allocation happens when the sys.buffalloc method is used. The socket is unable to TX data if its TX buffer has 0 capacity. Actual current buffer capacity can be checked through the sock.txbuffsize which returns buffer capacity in bytes. Relationship between the two is as follows: sock.txbuffsize=num_pages*256-16 (or =0 when num_pages=0), where "num_pages" is the number of buffer pages that was GRANTED through the sock.txbuffrq. "-16" is because 16 bytes are needed for internal buffer variables.

Buffer allocation will not work if the socket port to which this buffer belongs is not idle (sock.statesimple is not at 0- PL_SSTS_CLOSED) at the time when sys.buffalloc executes. You can only change buffer sizes of sockets that are idle.