Which design is best from a performance point of view?

Question

Hello
I'm writing a small system that needs to track changes to certain columns on 4 different tables. I'm using triggers on those columns to write the changes to a single "change register" table, which has 12 columns. Beacuse the majority of tracked data is not shared between the tables, most of the columns will have null values. From a design point of view it is apparent that having 4 separate change register tables (one for each main table that is being tracked), would be better in terms of avoiding lots of null columns for each row, but I was trying to trade this off against having a single table to see all changes that have been made across the tracked tables.
From a performance point of view though, will there be any real difference whether there are 4 separate tables or 1 single register table? I'm only ever going to be inserting into the register table, and then reading back from it at a later date and there won't be any indexes on it. Someone I work with suggested that there would be more overhead on the redo logs if a single table was used rather than 4 separate tables.
Any help would be appreciated.
David

Answer 1

The volumes of data are going to be pretty small,
maybe a couple of thousand records each day, it's an
OLTP environment with 150 concurrent users max.Consider also the growing of data and if you'll put data constantly to an historical db or if the same tables will contain the increasing number of record.
The point that my colleague raised was that multiple
inserts into a single table across multiple
transactions could cause a lot of redo contention,
but I can't see how inserting into one table from
multiple triggers would result in more redo
contention that inserting into multiple tables. The
updates that will fire the triggers are only ever
going to be single row updates, and won't normally
cause more than one trigger to fire within a single
transaction. Is this a fair assumption to make?
David
I agree with you, the only thing I will consider, instead of redo problem, is the locking on the table that could be generated when logs of different tables will have to be put in a single table, i mean if after insert of a log record you could need to update it....
In this case if 2 or more users have to update the same log you could have problems.