Despite the title, this is actually a technical post about Oracle, disk I/O and Exadata & Oracle In-Memory Database Option performance. Read on :)
If a car dealer tells you that this fancy new car on display goes 10 times (or 100 or 1000) faster than any of your previous ones, then either the salesman is lying or this new car is doing something radically different from all the old ones. You don’t just get orders of magnitude (more...)
I have been teaching the Enkitec Exadata Administration Class this week and made an interesting observation I thought was worth sharing with regards to IO Resource Management on Exadata.
I have created a Database Resource Manager (DBRM) Plan that specifically puts a resource consumer group to a disadvantage. Actually, quite severely so but the following shouldn’t be a realistic example in the first place: I wanted to prove a point. Hang-on I hear you say: you (more...)
(the details are investigated and specific to Oracle’s database implementation on Linux x86_64)
Exadata IO: This event is not used with Exadata storage, ‘cell single block physical read’ is used instead.
Despite p3 listing the number of blocks, I haven’t seen a db file sequential read event that read more than one block ever. Of course this could change in a newer release.
One of the important things (more...)
I’m sharing this in the hope of saving someone from an unwelcome surprise.
I recent upgraded an Exadata system from 18.104.22.168.1 to 22.214.171.124.1. Apart from what turns out to be a known bug that resulted in the patching of the InfiniBand switches “failing”, it all seemed to go without a snag. That’s until I decided to do some node failure testing…
Having forced a node (more...)
Just a quick post on a new Exadata feature called Zone Maps. They’re similar to storage indexes on Exadata, but with more control (you can define the columns and how the data is refreshed for example). People have complained for years that storage indexes provided no control mechanisms, but now we have a way to exert our God given rights as DBA’s to control yet another aspect of the database. Here’s a link to the (more...)
Recently I’ve noticed the occasional thread in Oracle newsgroups and lists asking about hugepages support in Linux, including ‘best practices’ for hugepages configuration. This information is out on that ‘world-wide web’ in various places; I’d rather put a lot of that information in this article to provide an easier way to get to it. I’ll cover what hugepages are, what they do, what they can’t do and how best to allocate them for your particular (more...)
Oracle is announcing today what it’s calling “Oracle Big Data SQL”. As usual, I haven’t been briefed, but highlights seem to include:
- Oracle Big Data SQL is basically data federation using the External Tables capability of the Oracle DBMS.
- Unlike independent products — e.g. Cirro — Oracle Big Data SQL federates SQL queries only across Oracle offerings, such as the Oracle DBMS, the Oracle NoSQL offering, or Oracle’s Cloudera-based Hadoop appliance.
- Also unlike independent (more...)
As part of my series on the keys to and likelihood of success, I outlined some examples from the DBMS industry. The list turned out too long for a single post, so I split it up by millennia. The part on 20th Century DBMS success and failure went up Friday; in this one I’ll cover more recent events, organized in line with the original overview post. Categories addressed will include analytic RDBMS (including data (more...)
Last week I’ve gotten a question on how storage indexes (SI) behave when the table for which the SI is holding data is changed. Based on logical reasoning, it can be two things: the SI is invalidated because the data it’s holding is changed, or the SI is updated to reflect the change. Think about this for yourself, and pick a choice. I would love to hear if you did choose the correct one.
I know, posts about up-coming user group meetings are not exactly exciting, but it’s good to be reminded. You can’t beat a bit of free training, can you?
On Monday 14th I am doing a lightning talk at the 4th Oracle Midlands event. The main reason to come along is to see Jonathan Lewis talk about designing efficient SQL and then he will also do a 10 minute session on Breaking Exadata (to achieve that (more...)
Anyone who has looked at Exadata might ask the question, and I did so too. After all, cell smart table scan is in wait class User IO so there should be more, right? This is what you find for a smart scan:
NAME PARAMETER1 PARAMETER2 PARAMETER3 WAIT_CLASS ------------------------------ -------------------- -------------------- ------------------------------ --------------- cell smart table scan cellhash# User I/O cell smart index scan cellhash# User I/O
Compare this to the traditional IO request:
NAME PARAMETER1 PARAMETER2 (more...)
I recently was involved in an investigation on a slow-running report on an Exadata system. This was rather interesting, the raw text file with the query was 33kb in size, and SQL Developer formatted the query to > 1000 lines. There were lots of interesting constructs in the query and the optimiser did its best to make sense of the inline views and various joins.
This almost lead to a different post about the importance (more...)
At the Accenture Enkitec Group we have a couple of Exadata racks for Proof of Concepts (PoC), Performance validation, research and experimenting. This means the databases on the racks appear and vanish more than (should be) on an average customer Exadata rack (to be honest most people use a fixed few existing databases rather than creating and removing a database for every test).
Nevertheless we gotten in a situation where the /etc/oratab file was not (more...)
Here’s a little known feature of Exadata – you can use a Bloom filter computed from a join column of a table to skip disk I/Os against another table it is joined to. This not the same as the Bloom filtering of the datablock contents in Exadata storage cells, but rather avoiding reading in some storage regions from the disks completely.
So, you can use storage indexes to skip I/Os against your large fact table, based on a (more...)
I guess everybody who is working with Oracle databases and has been involved with Oracle Exadata in any way knows about smartscans. It is the smartscan who makes the magic happen of full segment scans with sometimes enormously reduced scan times. The Oracle database does smartscans which something that is referred to as ‘offloading’. This is all general known information.
But how does that work? I assume more people are like me, and are anxious (more...)
Enkitec is the best consulting firm for hands on implementation, running and troubleshooting your Oracle based systems, especially the engineered systems like Exadata. We have a truly awesome group of people here; many are the best in their field (just look at the list!!!).
This is why I am here.
There are already a lot of blogposts and presentations done about Hybrid Columnar Compression and i am adding one more blogpost to that list. Recently i was doing some small tests one HCC and noticed that that inserts on a HCC row didn’t got compressed and yes i was using direct path loads:
DBA@TEST1> create table hcc_me (text1 varchar2(4000)) compress for archive high; Table created. KJJ@TEST1> insert /*+ append */ into hcc_me select dbms_random.string('x',100) (more...)
We have been migrating our databases from the non-Exadata servers to the Exadata Database Machine using the “RMAN 11g Duplicate standby from Active database” command, to create the standby databases on the Exadata machine. Below are the steps which were performed for these successful migrations. Assumptions Here we assume that the following tasks has been […]