Oracle updating large tables
Below is the Router Group Filter Condition and you can see how the mapping looks like in the below image (Below mapping image has not any transformation logic in it).
However , it will take a lot of time(and resource) if you use the 'clasy' way ! Sure -- disable all constraints against the table, do a CREATE TABLE AS SELECT that creates the modified table, drop the existing table, rename the new table to the old table, then re-enable constraints.
redo - yes temp - I dont think its going to use temp because no sorting will happen rbs - I'm afraid no.
Note, parallel execution is not a silver bullet, and may not efficient in all cases. Also, I'd double check the efficiency of the functions involved.
Would it be possible to rewrite them the way to minimize number of calls ?
We discussed about a design approach for this scenarion in one of our prior articles.
Here in this updated article lets discuss a different approach to update Larger tables using Informatica Mapping.
Many a times, you come across a requirement to update a large table in SQL Server that has millions of rows (say more than 5 millions) in it.
In this article I will demonstrate a fast way to update rows in a large table Consider a table called which has more than 5 millions rows.
Suppose you want to update a column with the value 0, if it that column contains negative value.
Let us also assume that there are over 2 million row in that column that has a negative value.
"Usually" is an important word here: check it out in a test environment to confirm for your data.