Oracle

Oracle recycle bin flashback table feature

When you do ‘Select * from tab;’ some times, you will be surprised to see some tables with garbage names. Welcome to the world of Oracle Recycle Bin Feature. Because of this feature, Oracle saves the dropped table in recycle bins until you clear it. 1. Empty recycle bin use the command: PURGE RECYCLEBIN; 2. […]

Aggregate aware queries

Imagine a scenario table having 20 million transactions for 10 years and a user writing a query to get data aggregated at monthly level. The best guess for the time required to return the result set, even after extensive database tuning can be in multiples of 10 minutes or even an hour. What is the […]

Why Informatica sequences & Sybase/SQL server identity columns, should not be used?

Informatica provides the sequence object to create surrogate keys during load. These object is also sharable within various mappings hence can be used in parallel. But I will recommend never using it.  Here’s the Reason why…. 1. MIGRATION ISSUE:  The sequence is stored in the Informatica repository. That means it is disconnected from the target […]

Slow Running ETL process (read side) & Table Statistics (Oracle).

Sometimes an ETL process runs considerably slow speed. During test for the small result set it might fly but when a million rows are applied the performance takes a nosedive. There can be many reasons for slow ETL process.  The process can be slow because read, transformation, load. Lets eliminate the transformation and load for […]