Using Timestamps as Unique Keys

July 17, 2002 Timothy Prickett Morgan

Hey, Ted:

We need to generate unique keys for each record written to a file and thought that the timestamp would make a good unique key for a file. Then we ran into a problem. The RPG TIME op code fills in only the first three digits of the microseconds portion of a timestamp field. The last three digits are always zeros.

Is there another way in RPG to fill the timestamp with a unique time, such as an op code that fills the last three digits as well?

— Michael

Since your concern is that you have a unique value, not that you have an accurate timestamp, let me suggest an alternate approach. Compare the timestamp to the timestamp that was retrieved for the previous record. If they are the same, add one microsecond to get a unique key value.

D key             s               z                     
D timestamp       s               z                     
D timestampsave   s               z                     

C                time                    timestamp   
C                if        timestamp <> timestampsave
C                eval      key = timestamp           
C                eval      timestampsave = timestamp 
C                else                                
C                adddur    1:*mseconds   key         
C                endif                               

— Ted

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