createUserSessions - как работает?

[Logger]

А вот код хранимки
Отформатирован тут
https://sqlformat.org/

CREATE PROCEDURE [dbo].[CREATEUSERSESSIONS] @clientType int, @sessionType int, @serverid int, @versionid int, @userid nvarchar(8),
                                                                                                                      @lanExt nvarchar(10),
                                                                                                                              @manExt nvarchar(10),
                                                                                                                                      @computerName nvarchar(80),
                                                                                                                                                    @sid nvarchar(124),
                                                                                                                                                         @recid bigint, @startId int, @maxusers int, @licenseType int, @masterId int, @maxClientId int, @dataPartition nvarchar(8),
                                                                                                                                                                                                                                                                       @sessionid int OUTPUT,
                                                                                                                                                                                                                                                                                      @loginDateTime datetime OUTPUT AS DECLARE @return_val AS int DECLARE @first AS int DECLARE @max_val AS int DECLARE @counter AS int BEGIN
SELECT @sessionid = -1
SELECT @max_val = -1
SELECT @counter = 0
SELECT @loginDateTime = dateadd(ms, -datepart(ms, getutcdate()), getutcdate()) if(NOT exists
                                                                                    (SELECT *
                                                                                     FROM SYSSERVERSESSIONS WITH (NOLOCK)
                                                                                     WHERE SERVERID = @serverid
                                                                                       AND Status = 1)) BEGIN
SELECT @sessionid = -2 RETURN END
SELECT @first = min(SESSIONID)
FROM SYSCLIENTSESSIONS WITH (UPDLOCK,
                             READPAST)
WHERE STATUS = 0
  AND SESSIONID > @maxClientId
  AND SESSIONID <> @masterId IF
    (SELECT count(*)
     FROM SYSCLIENTSESSIONS
     WHERE SESSIONID IN (@first)) > 0 BEGIN IF (@licenseType = 0) BEGIN
  UPDATE SYSCLIENTSESSIONS
  SET STATUS = 1,
      VERSION = @versionid,
                SERVERID = @serverid,
                USERID = @userid,
                LOGINDATETIME = @loginDateTime,
                SID = @sid,
                USERLANGUAGE = @lanExt,
                HELPLANGUAGE = @manExt,
                CLIENTTYPE = @clientType,
                SESSIONTYPE = @sessionType,
                CLIENTCOMPUTER = @computerName,
                DATAPARTITION = @dataPartition
  WHERE SESSIONID IN (@first) END ELSE IF (@licenseType = 1) BEGIN
  UPDATE SYSCLIENTSESSIONS
  SET STATUS = 1,
      VERSION = @versionid,
                SERVERID = @serverid,
                USERID = @userid,
                LOGINDATETIME = @loginDateTime,
                SID = @sid,
                USERLANGUAGE = @lanExt,
                HELPLANGUAGE = @manExt,
                CLIENTTYPE = @clientType,
                SESSIONTYPE = @sessionType,
                CLIENTCOMPUTER = @computerName,
                DATAPARTITION = @dataPartition
  WHERE SESSIONID IN (@first)
    AND (
           (SELECT count(SESSIONID)
            FROM SYSCLIENTSESSIONS
            WHERE CLIENTTYPE = @clientType
              AND ((STATUS = 1)
                   OR (STATUS = 2))) < @maxusers) END ELSE IF (@licenseType = 2) BEGIN
  UPDATE SYSCLIENTSESSIONS
  SET STATUS = 1,
      VERSION = @versionid,
                SERVERID = @serverid,
                USERID = @userid,
                LOGINDATETIME = @loginDateTime,
                SID = @sid,
                USERLANGUAGE = @lanExt,
                HELPLANGUAGE = @manExt,
                CLIENTTYPE = @clientType,
                SESSIONTYPE = @sessionType,
                CLIENTCOMPUTER = @computerName,
                DATAPARTITION = @dataPartition
  WHERE SESSIONID IN (@first)
    AND (
           (SELECT count(SESSIONID)
            FROM SYSCLIENTSESSIONS
            WHERE CLIENTTYPE = @clientType
              AND (USERID = @userid)
              AND ((STATUS = 1)
                   OR (STATUS = 2))) > 0
         OR
           (SELECT count(DISTINCT USERID)
            FROM SYSCLIENTSESSIONS
            WHERE CLIENTTYPE = @clientType
              AND ((STATUS = 1)
                   OR (STATUS = 2))) < @maxusers) END IF @@ROWCOUNT = 0
  SELECT @sessionid = 0 ELSE
  SELECT @sessionid = @first END ELSE BEGIN IF (@licenseType = 1) BEGIN IF
    (SELECT count(SESSIONID)
     FROM SYSCLIENTSESSIONS
     WHERE CLIENTTYPE = @clientType
       AND ((STATUS = 1)
            OR (STATUS = 2))) >= @maxusers
  SELECT @sessionid = 0 END ELSE IF (@licenseType = 2) BEGIN IF ((
                                                                    (SELECT count(DISTINCT USERID)
                                                                     FROM SYSCLIENTSESSIONS
                                                                     WHERE CLIENTTYPE = @clientType
                                                                       AND ((STATUS = 1)
                                                                            OR (STATUS = 2))) >= @maxusers)
                                                                 AND (
                                                                        (SELECT count(SESSIONID)
                                                                         FROM SYSCLIENTSESSIONS
                                                                         WHERE CLIENTTYPE = @clientType
                                                                           AND (USERID = @userid)
                                                                           AND ((STATUS = 1)
                                                                                OR (STATUS = 2))) = 0))
  SELECT @sessionid = 0 END IF (@sessionid = -1)
  OR (@licenseType = 0) BEGIN WHILE (@sessionid = -1
                                     AND @counter < 5) BEGIN
  SET @counter = @counter + 1 IF
    (SELECT count(SESSIONID)
     FROM SYSCLIENTSESSIONS WITH (UPDLOCK)
     WHERE STATUS = 0
       OR STATUS = 1
       OR STATUS = 2
       OR STATUS = 3) = 0
  SELECT @max_val = @startId ELSE
  SELECT @max_val = max(SESSIONID)+1
  FROM SYSCLIENTSESSIONS WITH (UPDLOCK) IF (@max_val > 65535)
  SELECT @sessionid = -3 ELSE BEGIN
  INSERT INTO SYSCLIENTSESSIONS(SESSIONID, SERVERID, VERSION, LOGINDATETIME, USERID, SID, USERLANGUAGE, HELPLANGUAGE, CLIENTTYPE, SESSIONTYPE, RECID, CLIENTCOMPUTER, STATUS, DATAPARTITION)
  VALUES(@max_val,
         @serverid,
         @versionid,
         @loginDateTime,
         @userid,
         @sid,
         @lanExt,
         @manExt,
         @clientType,
         @sessionType,
         @recid,
         @computerName,
         1,
         @dataPartition) IF @@ROWCOUNT = 0 BEGIN
  SELECT @sessionid = -1 END ELSE
  SELECT @sessionid = @max_val END END END END END