INF: Determining User Segments from Segmap Values

  - Microsoft SQL Server version 4.2 for OS/2
  - Microsoft SQL Server version 4.2

SUMMARY

This article describes a stored procedure which can be used to determine which user segments map to a Microsoft SQL Server device based on the values from the master.dbo.sysusages segmap column.

MORE INFORMATION

One difficulty in administering databases in which user segments have been defined is determining which segments map to each database device.

Each user segment in a database is assigned a segment number unique in that database, this number is recorded in the dbo.syssegments table in each database. The master.dbo.sysusages table indicates how each database maps to its devices. The segmap column in the sysusages table holds the information about which segments map onto each device.

The stored procedure has been kept simple so that users can run it even in new systems to which they have not yet migrated user databases. The syntax is:

   execute sp_segmap <segmap value>

Example

For an example of sp_segmap's use, assume that a database has one line in sysusages which has a segmap value of 7.

   execute sp_segmap 7

Type the following into a file segmap.sql:

use master go if exists (select * from sysobjects

                where name = 'sp_segmap')
  drop procedure sp_segmap

create procedure sp_segmap @segmap int as

create table #seg

      (segment_num int NULL)

if @segmap = 0

/* no segments mapped */

  insert #seg values(NULL)
  select * from #seg
  order by segment_num
  return

while (@segnum < 30) begin

  if (@segmap & @pattern) != 0
    insert #seg values(@segnum)
  select @pattern = @pattern * 2
  select @segnum = @segnum + 1

/* Test final bit in @pattern */

  insert #seg values(@segnum)

/* Test if segment 31 bit on */

  insert #seg values(31)

grant execute on sp_segmap to public go

Run segmap.sql in isql as the sa user:

isql /Usa /P<password> /S<server> /e /isegmap.sql /osegmap.sql