In the first intallment, Redo that History!, we talked about how redo logs contain the history of transactions in the Oracle database. With this next intallment, let’s continue and talk about the redo log’s cousin, the archive log. Simply put, the archive log is an old redo log. Archive logs are extremely useful to recover the […]
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Snappy title, huh?
Aka: Why a sql plan baseline may be no guarantee of stability.
The other day, a problematic plan flip…
Cue much discussion about plan flips etc.
My thoughts on stability are that the priority for most application owners is stability and predictability but that does not tally with the defaul CBO behaviour and potentially you have to turn off a helluva lot to even get close.
Plan degradations on upgrade are normal.
This one’s no different.
On further investigation, turned out application was setting optimizer_mode = first_rows somewhere.
First point about this is that first_rows really shouldn’t be used either as a hint or as an optimizer_mode.
What does FIRST_ROWS mean?
From 11g doco:
Oracle SOA Suite 11g (18.104.22.168) environment is connected to a database which is its dehydration store database, used to store process status data, especially for asynchronous BPEL processes. Production environments tend to produce millions of records in tables of that database. This, when not well maintained, can become a true performance bottleneck in the database and SOA Suite engine itself. Some […]
I’ve lost track of the number of times I see this sequence (no pun intended) of actions in code:
SELECT my_sequence.nextval INTO :some_variable FROM dual;
INSERT INTO my_table VALUES (:some_variable, ....);
My question is always “Why?” What was it that made you so desperate in need of that sequence value that you needed it before you inserted it ? It is simply, easier, and more efficient just to get it back from the insert statement itself.
Oracle Executive Vice President John Fowler used the occasion of Open World 2015 to introduce Oracle's SPARC M7 processor, the fastest in the world. Learn more ...
Sometimes I need to import printed documents like contracts, letters and so on, but I must say that until yesterday my attempts to successfully scan these stuff with online OCR services had gone badly.
Most of the times, in the past, the number of wrong words, letters converted into numbers, typically "l"s would become "1"s, "O"s would be turned into "0"s, "A"s into "4"s, quickly led me to