RE: Fastest way to delete records.

["Sims, Ken" <KSIMS@xxxxxxxxxxxxxxxx>]

Hi Quazy -

>I have a file with about 10 million records.  It is keyed on  
>Company #, Employee #, and Time stamp.
>
>I need to delete all records that have a time stamp before a 
>certain time period.
>
>Any suggestions on the fastest approach?
>Speed is a very important factor. 

In addition to suggestions already made, another possibility if you are
deleting less records than you are keeping is to read through the file using
the keys as described above.  If the time stamp indicates that the record is
eligible for deletion, delete it.  If not, then there will not be any
further records to delete for this company/employee combination, so do a
SETGT with a KLIST specifying the company/employee.  This will skip reading
the rest of the record for this company/employee.  The next READ will read
the first record for the next company/employee.

This way you skip through the file, reading no more than one ineligible
record per company/employee combination.  For example, if there are
10,000,000 records in the file of which 1,000,000 records are to be deleted,
and 10,000 different company/employees, then you will not read more than
1,010,000 records and will skip at least 8,990,000 records.  If there are
company/employees with no records to keep, then you skip even more records.

As you can see, the less number of unique company/employee combinations you
have, the better this method works.

Ken
Southern Wine and Spirits of Nevada, Inc.
Opinions expressed are my own and do not necessarily represent the views of
my employer or anyone in their right mind.

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