SMS Unique ID (SMSID) Allocation

• Microsoft Systems Management Server versions 1.0, 1.1, and 1.2

SUMMARY

Every client in a Microsoft Systems Management Server site has a unique identification called an SMSID. This is derived from the Unique ID (UID) file on a logon server. Systems Management Server performs several functions to ensure uniqueness within the site as well as across sites. This article discusses these functions in detail.

MORE INFORMATION

Systems Management Server performs the following functions to ensure uniqueness within the site and across sites:

• To ensure uniqueness (in the event a site is uninstalled), the last UID range is saved from the Registry by Systems Management Server Setup and placed into the site server's Sms.ini file. If a site is reinstalled later, this range is restored to the Registry, thus the site does not allocate any duplicate SMSIDs. If the Sms.ini is removed from the site server following an uninstall, each client should be uninstalled and reinstalled.
• It is possible to reinstall the site and ensure that no duplicate SMSIDs are allocated. As the last allocated UID range is stored in the registry, the Administrator, in lieu of uninstalling and reinstalling client computers, can place a sufficiently high value in the registry to ensure that duplicate SMSIDs are not issued. The registry entry is stored as a REG_SZ type in the following key:

        HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\Components
        \SMS_MAINTENANCE_MANAGER\Next SMS Unique ID
  

  NOTE: The above registry key is one path; it has been wrapped for readability.

• Assuming that the site is installed, normal processing begins. In creating the actual UID file, the SMSID is managed in several parts. The first three characters are always the site code of the creating site. The next two characters represent the UID range and allows each logon server to own a range of SMSIDs to allocate to clients. No two logon servers will have the same range. The last three characters are sequentially incremented each time an SMSID is allocated by a client. The numeric range of the SMSID is expanded by including the A to Z characters as extensions of 0 to 9 range. This provides 36 values instead of just 10, and allows for the following maximum capacities:

      - Unique site codes: 36^3 =     46,656
  
      - Unique logon server ranges:
  
        - Assuming not more than 44,065 clients per logon server:
  
             36^2 =   1,296
  
        - Assuming more than 44,065 clients per logon server is more
          complicated because each doubling of 44,065 SMSIDs per server
          reduces the available ranges by half.
  
        Unique SMSIDs per logon server (depends on number of logon servers
        because values between the two bounds of 1 and 1,296 vary the number
        of available ranges which can be allocated upon the expiration of a
        prior range):
  
        - Assuming a single logon server: 36^5 =       60,466,176
  
        - Assuming 1,296 logon servers:   36^4 =        1,679,616
  
      - Unique SMSIDs (per site):   36^5 =       60,466,176
  
      - Unique SMSIDs (total):      36^8 =   78,364,164,096
  
  

• When each new client attempts to allocate an SMSID, it takes the current name of the UID file as its own SMSID and attempts to increment the name of the UID file to the next value. The time stamp for the UID does not change when a client is installed. Each client does this in turn (it is not controlled by the site server). Only the allocation of new ranges is managed by the site server. When a sharing violation or other errors occur, the client will retry 30 times, and indicate a # character on the screen for each retry. The UID file is maintained in a single location, SMS_SHR\SMSID\<next_smsid>.UID.
• The Maintenance Manager compares each logon server's UID range to evaluate if a new range needs to be issued. If the current value of the SMSID exceeds "*****Y00" (44,065 SMSIDs), a new range is allocated to the logon server. This is a rather proactive threshold (2,591 SMSIDs early), intended to make sure the range never actually expires even when Maintenance Manager is set for the slow response setting in site properties. This provides room for 44,065 computers per range, and will have a minor effect on the architectural limitations described above.
• If a computer moves from one site to another by virtue of three successive logons to a new site's domain, then the original SMSID for the client is used by the new site database. This is by design. The SMSID should not be altered after it is allocated. The uninstall and/or reinstall procedures should be used when a SMSID change is required on a client.