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.
This is also why Accenture approached us some time ago – and you may already have seen today’s announcement that Enkitec got bought!
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;
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 […]
The post Migrating a Database to an Exadata Machine appeared first on VitalSoftTech.
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/18.104.22.168/grid/bin/crsctl stop crs” to get everything down (more...)
Yes that is true, i said it, cellcli can lie to you there are some special cases were the output of cellcli is not the reality and you should double check it’s output with your standard OS tools. So this the output if dcli calling cellcli on an Exadata rack from an client:
[root@dm01db01 ~]# dcli -g cell_group -l root cellcli -e list cell attributes cellsrvStatus,msStatus,rsStatus
dm01cel01: running running running
dm01cel02: running running running
We had a client that was running into a strange issue on their Exadata where new connections coming in through the SCAN were failing. After doing some troubleshooting, it was discovered that it was related to one of the SCAN listeners not properly accepting requests from new sessions. The VIP and listener were running, and everything looked normal.
We had the following SCAN setup:
On Exadata the local drives on the compute nodes are not big enough to allow larger exports and often dbfs is configured. In my case I had a 1.2 TB dbfs file system mounted under /dbfs_direct/.
While I was doing some exports yesterday I found that my dbfs wasn’t mounted, running quick crsctl command to bring it online failed:
[oracle@exadb01 ~]$ crsctl start resource dbfs_mount -n exadb01
CRS-2672: Attempting to start 'dbfs_mount' on 'exadb01'
On Exadata (or when setting cell_offload_plan_display = always on non-Exadata) you may see the storage() predicate in addition to the usual access() and filter() predicates in an execution plan:
SQL> SELECT * FROM dual WHERE dummy = 'X';
Check the plan:
Display execution plan for last statement for this session from library cache...
SQL_ID dtjs9v7q7zj1g, child number 0
SELECT * FROM dual WHERE dummy = 'X'
Most people are relating direct path reads with an algorithm which is just controlling the way our read is performed. But actually in Exadata environment this is the algorithm which is balancing the load between the Compute and the Storage nodes. Something really important. As usual, the algorithm is not perfect and for some situations […]
If you try to find out what is HCC and how it works you could start reading the documentation, then some books, blog posts and at the end you will have to put all together. In this post I’ll do exactly this. Put all together. Starting with the basic and going through the internals with […]
I’ve previously written about a problem I encountered when kdump is configured to write to an NFS location with UEK (in Exadata software version 22.214.171.124.1). I’m please to report that the root cause of the problem has been identified and there is a very simple workaround.
There were some frustrating times working this particular SR, the most notable being a response that was effectively, “It works for me (and so I’ll (more...)
I seem to be getting a lot of surprising performance results lately on our X-2 quarter rack Exadata system, which is good – the result you don’t expect is the one that teaches you something new.
This time, I was looking at using a temporary tablespace based on flash disks (more...)
Oracle has released the much-anticipated version of cellsrv compatible with Oracle Database 126.96.36.199 (patch #16980054). Before thinking about upgrading, read MOS note #1571789.1 carefully. Unless you are planning to run database 12c on your Exadata, it would be advisable to continue down the 11.2 branch (more...)
Today, Oracle announced the Exadata X4-2 model. The X4 has some considerable improvements, namely:
- 12-core Intel Xeon e5-2697 CPUs, up from the 8-core models found in the X3-2 (hello, database licenses!)
- 256GB RAM per database server, upgradeable to 512GB
- 96GB RAM per storage server
- 800GB Sun Flash F80 cards (more...)
Exadata Maximum Availability Architecture from Yunus Emre Baransel
There were problems that affected UEK and NFS when 188.8.131.52.1 was initially released (as covered by Andy Colvin). As mentioned in the comments of Andy’s post: Oracle released an updated ISO with fixes for this problem (patch 16432033).
There were also problems with kdump not (more...)
Recently we noticed that imageinfo was displaying the following information at a customers site. Imageinfo was not displaying data i suspected, so a quick little blogpost about what was going on there.
[root@dm01db01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/dbs_group -l root "imageinfo | grep 'Image version'"
dm01db01: Image version: 11.2. (more...)
Of all the claims I make about SSD for Oracle databases, the one that generates the most debate is that placing redo logs on SSD is not likely to be effective. I’ve published data to that effect in particular see Using SSD for redo on Exadata - pt 2 (more...)