sn_a_lt_b
if (sn_a_lt_b(ccb->ccb_CmdSN, sess->s_ExpCmdSN)) {
if (sn_a_lt_b(sess->s_ExpCmdSN, ExpCmdSN))
if (sn_a_lt_b(sess->s_MaxCmdSN, MaxCmdSN))
sn_a_lt_b(sn, ccb->ccb_CmdSN) &&
if (!sn_a_lt_b(buff->sernum[b], num))
if (!sn_a_lt_b(num, buff->ExpSN))