RE: READ PREVOIUS in CLP

In Ye Olden Dayes (back in the S/38 world) the general consensus was
that "Logical Files Degrade System Performance." I used to espouse this
idea myself. The reason was that the system had to keep all of the
index trees properly pruned; this took time.

So a balance would be struck between ease of application programming
using a new index versus the time it took to maintain that index at all
times. If the keys were not unique, you could defer the access path
maintenance until the file was actually used-- ie if an index is only
used once a month during month ending, why bother keeping it up to date
between times?

You can still specify MAINT(*IMMED|*DLY|*REBLD) as needed.

With the improved performance of OS/400 and its descendants this is no
longer as big an issue as it once was-- we have several files with over
40 LFs and Views. Don't ask if we need them all-- no one wants to
compare keys and see which ones are redundant. And the system does a
fairly decent job of sharing the access path when appropriate.

Unless you're writing thousands of records to a file at once the
maintenance of all the indices is barely noticable.

Paul E Musselman