Oracle database operating system memory allocation management for PGA – part 3: Oracle 11.2.0.4 and AMM: Quiz

This is a series of blogposts on how the Oracle database makes use of PGA. Earlier posts can be found here (PGA limiting for Oracle 12) and here (PGA limiting for Oracle 11.2).

Today a little wednesday fun: a quiz.

What do you think will happen in the following situation:

-Oracle Linux x86_64 6u6.
-Oracle database 11.2.0.4 PSU 4
-Oracle database (single instance) with the following parameter set: memory_target=1G. No other (more...)

Oracle database operating system memory allocation management for PGA – part 2: Oracle 11.2

This is the second part of a series of blogpost on Oracle database PGA usage. See the first part here. The first part described SGA and PGA usage, their distinction (SGA being static, PGA being variable), the problem (no limitation for PGA allocations outside of sort, hash and bitmap memory), a resolution for Oracle 12 (PGA_AGGREGATE_LIMIT), and some specifics about that (it doesn’t look like a very hard limit).

But this leaves out Oracle version (more...)

Oracle database operating system memory allocation management for PGA

This post is about memory management on the operating system level of an Oracle database. The first question that might pop in your head is: isn’t this a solved problem? The answer is: yes, if you use Oracle’s AMM (Automatic Memory Management) feature, which let’s you set a limit for the Oracle datababase’s two main memory area’s: SGA and PGA. But in my opinion any serious, real life, usage of an Oracle database on Linux (more...)

UKOUG Tech14 slides – Exadata Security Best Practices

I think 2 years is long enough to wait between posts!

Today I delivered a session about Oracle Exadata Database Machine Best Practices and promised to post the slides for it (though no one asked about them :). I’ve also posted them to the Tech14 agenda as well.

Direct download: UKOUG Tech14 Exadata Security slides

The Importance of the In-Memory DUPLICATE Clause for a RAC System

With the INMEMORY clause you can specify 4 sub-clauses:

  • The MEMCOMPRESS clause specifies whether and how compression is used
  • The PRIORITY clause specifies the priority (“order”) in which the segments are loaded when the IMCS is populated
  • The DISTRIBUTE clause specifies how data is distributed across RAC instances
  • The DUPLICATE clause specifies whether and how data is duplicated across RAC instances

The aim of this post is not to describe these attribues in detail. Instead, (more...)

12.1.0.2 Introduction to Zone Maps Part II (Changes)

In Part I, I discussed how Zone Maps are new index like structures, similar to Exadata Storage Indexes, that enables the “pruning” of disk blocks during accesses of the table by storing the min and max values of selected columns for each “zone” of a table. A Zone being a range of contiguous (8M) blocks. I […]

Exadata Shellshock: IB Switches Vulnerable

Andy Colvin has the lowdown on the Oracle response and fixes for the bash shellshock vulnerability.

However, when I last looked it seemed Oracle had not discussed anything regarding the IB switches being vulnerable.

The IB switches have bash running on them and Oracle have verified the IB switches are indeed vulnerable.


[root@dm01dbadm01 ~]# ssh 10.200.131.22

root@10.200.131.22's password:

Last login: Tue Sep 30 22:46:41 2014 from dm01dbadm01.e-dba.com

 (more...)

Exadata and Bash Shellshock

There has recently been a lot of news about the exploit revealed in the bash shell.  While the fix is very quick to implement, there are a couple of tricks that are required to install this update on an Exadata environment.  According to Oracle support note #1405320.1, Exadata storage server versions 11.2.3.x.x and 12.1.1.x.x are susceptible to the exploit.  On a typical Oracle Enterprise Linux, a simple (more...)

Exadata: What’s Coming

This is based on the presentation Juan Loaiza gave regarding What’s new with Exadata. While a large part of the presentation focussed on what was already available, there are quite a few interesting new features that are coming down the road.

First of was a brief mention of the hardware. I’m less excited about this. The X4 has plenty of the hardware that you could want: CPU, memory and flash. You’d expect some or all (more...)

ASM Diskgroup shows USABLE_FILE_MB value in Negative

Today while working on ASM diskgroup i noticed Negative value for USABLE_FILE_MB. I was little surprised as it has been pretty long that i worked on ASM. So i started looking around for blogs and mos docs and found few really nice one around. A negative value for USABLE_FILE_MB means that you do not have [&hellip

About index range scans, disk re-reads and how your new car can go 600 miles per hour!

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...)

12c HCC Row-Level Locking

In Oracle Database 12c we can find many new and shiny things… So many that we can miss the little good things really easy. I think that this one, is one of them. Previously I made a post “All About HCC“, describing how HCC is working and some of the issues that we can hit […]

Clobbering grub.conf is Bad

I’m sharing this in the hope of saving someone from an unwelcome surprise.

Background

I recent upgraded an Exadata system from 11.2.3.2.1 to 11.2.3.3.1. Apart from what turns out to be a known bug[1] 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...)

Exadata Zone Maps

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...)

The point of predicate pushdown

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...)

21st Century DBMS success and failure

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...)

Combining Bloom Filter Offloading and Storage Indexes on Exadata

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...)

Enkitec + Accenture = Even More Awesomeness!

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.

This is also why Accenture approached us some time ago – and you may already have seen today’s announcement that Enkitec got bought!

(more...)

Inserts on HCC tables

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...)

Database Shutdown With crsctl

I noticed something for the first time tonight when I was playing around in the Enkitec lab – something that I have been doing wrong for a while.  When working in the lab, I often rely on the crsctl command to shut down the entire cluster stack for me.  It’s really easy to use “crsctl stop cluster -all” followed by “dcli -l root -g ~/dbs_group /u01/app/11.2.0.4/grid/bin/crsctl stop crs” to get everything down (more...)