How much undo and redo does Oracle generate for different operations? More than you might think.
Buffer busy wait and related events can cripple performance of concurrent inserts. Bad in a single instance database, far worse in a RAC (think "gc buffer busy"). Often the problem is because of a primary key populated from a sequence. Reversing the index can fix this problem.
Concurrent inserts into a table will often result in crippling buffer busy wait problems as sessions serialize on access to the last block(s) of the table segment. Using hash clusters can remove the issue.
After more than 20 years of working with Oracle databases, I have recently found myself using SQL Server for the very first time. Until now, I have been a passive observer in the My-Database-Is-Better-Than-Yours wars, so it’s a pleasant change to be able to finally contribute.
I’m pleased to report that – as a software developer – the skills map pretty well between the databases.
Many people are terrified of global indexes, one reason being that partition DDLs on the table will either render them unusable, or take forever as they are updated. Deferred global index maintenance solves this, and should be an important driver for the 12c upgrade.
Why use interpreted PL/SQL when native compiled PL/SQL is so much faster? No reason at all - except that interpreted is the default, and most DBAs never change this. They should.
Can this parameter really boost performance? This simple test suggests that it can.
Unified Audit is a major architectural change: fast, easy, and impossible for the DBA to bypass. On upgrade to Oracle 12c, you really should enable it. The earlier method that we all use is pretty awful.
It is a frequently asked question in almost all the Oracle forums. There have had been numerous questions/posts regarding "But how to generate the trace file?" Well, it might seem a heck of a task, however, looking it step by step will make you understand that it is actually not that difficult.
Usually, database application developers do not have the required/necessary permissions/privileges to do all the steps that I will mention below. However, most of the steps could be done by application developer.
An important thing regarding function, you would agree with me that, at least once a PL/SQL developer must have heard that "A function MUST ALWAYS RETURN a VALUE of proper datatype".