RE: Fastest way to get a unique identifier/tracking column change s

["DeLong, Eric" <EDeLong@xxxxxxxxxxxxxxx>]

Charles,

As far as I can tell, UUID is supposed to be based on time and network
adapter (read MAC address), which is supposed to always be unique for any
network card.  I know the AS400 allows us to specify the network adapter MAC
address, but it never forgets the hardware address, so I ASSUME that GENUUID
would be grabbing the actual hardware MAC as opposed to the user assignable
MAC address.....  If not, then I see how two seperate servers *could*
potentially generate the same value, but it still seems unlikely.....

No, I didn't forget the old adage..... <g>

Eric DeLong
Sally Beauty Company
MIS-Project Manager (BSG)
940-898-7863 or ext. 1863



-----Original Message-----
From: CWilt@xxxxxxxxxxxx [mailto:CWilt@xxxxxxxxxxxx]
Sent: Monday, July 12, 2004 3:51 PM
To: midrange-l@xxxxxxxxxxxx
Subject: RE: Fastest way to get a unique identifier/tracking column
change s


Just a quick FYI, but GENUUID may not guarantee a unique ID.

Check out this thread in the newsgroup:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&threadm=9nu8eb.dt1.ln%40m
odula.bender-dv.de&rnum=1&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26selm
%3D9nu8eb.dt1.ln%2540modula.bender-dv.de

Seems as if duplicates can occur on a multi-processor system when multiple
processes are using it at the same time.
Unless it turned out to be a bug that was corrected.


HTH,
Charles


> -----Original Message-----
> From: Kevin Mohondro [mailto:kevin.mohondro@xxxxxxxxxxxxxxx]
> Sent: Monday, July 12, 2004 1:29 PM
> To: 'Midrange Systems Technical Discussion'
> Subject: RE: Fastest way to get a unique identifier/tracking column
> change s
> 
> 
> You could get a UUID (Universally Unique IDentifier). This 
> will give you a
> unique ID that you could use.
> 
> D getUUID         PR                  ExtProc('_GENUUID') 
> D  UUID_DS                        *   Value               
> 
> D UUID_DS         DS                                              
> D  BytPrv                       10u 0 Inz(%size(UUID_DS))
> D  BytAvl                       10u 0                             
> D  Hold                          8a   Inz(*allx'00')            
> D  UUID                         16a                               
> 
> C                   CallP     getUUID(%addr(UUID_DS))
> C                   Eval      Key = UUID                   
> 
> -Kevin
> -=-=-=-=-=-=-=-=-
> Kevin R Mohondro
> Programmer/Analyst
> Ashworth, Inc
> 
> -----Original Message-----
> From: Reeve Fritchman [mailto:reeve.fritchman@xxxxxxxxxx]
> Sent: Monday, July 12, 2004 7:22 AM
> To: 'Midrange Systems Technical Discussion'
> Subject: Fastest way to get a unique identifier/tracking 
> column changes
> 
> 
> I'm designing a new system with a requirement for detailed 
> tracking of, and
> inquiry into, column-level changes.  I've decided to build a 
> single file
> with before and after values, etc. for all the tables by 
> using triggers.
> Some of the tables have complex keys (order number/SKU/shipper
> location/consignee location/release number), and I don't want 
> to burden my
> historical tracking file with a nasty key structure to 
> support inquiry into
> the details of the changes.  I'm not going to track added records or
> date-of-last-change timestamps in the tables; the majority of 
> the changes
> will be on a limited number of columns (of the status and 
> date nature).
> 
>  
> 
> My design is to assign every row an "entity number"; the 
> entity number would
> be like a record serial number, would be unique on a 
> system-wide basis, and
> would be the key to the historical tracking table.  When a 
> user wants to see
> the details of the changes to a specific row, the row's 
> entity number would
> allow simple access to the tracking file.  Using SQL's AS 
> IDENTITY with the
> table name could work to provide a key to a specific record.
> 
>  
> 
> The challenge is to determine a way to get the entity number quickly.
> Having a control file is okay but probably limiting performance-wise;
> another possibility is a journaled data area.  Is there a system API
> providing a guaranteed unique sequential number?  Or is there a better
> approach for tracking column-level changes?
> 
>  
> 
> Thanks,
> 
> Reeve
> 
>  
> 
>  
> 
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