Restoring a Database to a New Diskgroup

I had the pleasure of rebuilding an Exadata rack for a customer a while back, and it provided a pretty good refresher in backup and recovery for me.  As DBAs, we back up databases all the time, but the restores are performed much less frequently.  In the case of this rack, there were several databases across multiple ASM diskgroups.  One of the goals of the rebuild was to consolidate all of the databases into a (more...)


        这篇文章主要从何时需要紧急修复、准备过程、实施阶段等几个方面来与大家分享Exadata 存储服务器Rescue方面的维护经验,有的地方提供了My Oracle Support网站的文章号。

了解storage server 和rescue方法

        首先,我们需要了解Exadata存储服务器(storage server)方面的知识,它主要提供智能的磁盘I/O给计算节点。关于磁盘的管理,可以通过阅读My Oracle Support文章Auto disk management feature in Exadata (Doc ID 1484274.1)来熟悉storage server上的自动磁盘管理特性。


何时需要Storage server(存储服务器)的rescue过程

        当系统盘失效,操作系统有一个文件系统损坏了或者boot区域被破坏了的时候。一台节点机上的两个系统磁盘都同时失效了的话,就必须通过CELLBOOT USB flash盘上的Oracle Exadata Storage Server软件进行rescue了。

请仔细阅读产品文档中的 Maintaining Exadata Storage Servers of Oracle Exadata Racks章节:
Using the Oracle Exadata Storage Server Software Rescue Procedure


        平时要查看CELLBOOT USB盘是否可用,如果丢失或者损坏了,通过如下过程来创建:
重新生成一个损毁的CELLBOOT USB闪存盘

        如果CELLBOOT USB闪存盘丢失或者损毁,您可以使用如下过程来创建一个新的。
注意: 针对运行Oracle Exadata Storage Server Software release或更高版本的机器创建一个USB闪存盘,要求机器操作系统版本是Oracle (more...)

Shrink/Grow Exadata diskgroups

One of the important tasks that I foresee after an initial Exadata deployment is, mostly prior to DB in production, is to balance/resize the Exadata diskgroups (DATA & RECO).  Generally, the space is distributed as 80(DATA), 20(RECO) or 40(DATA), 60(RECO), depending on the database backup option you choose while deploying. In one of our Exadata setups, we don't need such a huge RECO size, hence, we shrunk the RECO size and increased the DATA diskgroup (more...)

Oracle 12 and latches

Oracle DBAs who are so old that they remember the days before Oracle 11.2 probably remember the tuning efforts for latches. I can still recall the latch number for cache buffers chains from the top of my head: number 98. In the older days this was another number, 157.

But it seems latches have become less of a problem in the modern days of Oracle 11.2 and higher. Still, when I generate heavy (more...)

How long does a logical IO take?

This is a question that I played with for a long time. There have been statements on logical IO performance (“Logical IO is x times faster than Physical IO”), but nobody could answer the question what the actual logical IO time is. Of course you can see part of it in the system and session statistics (v$sysstat/v$sesstat), statistic name “session logical reads”. However, if you divide the number of logical reads by the total time (more...)

JSON support in Exadata and later

Some time ago Oracle announced that RDBMS has built-in support for JSON processing. A little later it was also mentioned that you have support for JSON in the Exadata storage servers for offloading. This is probably a lot more exciting to users of JSON than it is to me as I’m not a developer. However, whenever an announcement such as the one I’m referring to is made I would like to (more...)

Exadata’s onecommand fails to validate NTP servers on storage servers

This will be simple and short post on an issue I had recently. I got the following error while running the first step of onecommand – Validate Configuration File:

2015-07-01 12:31:03,712 [INFO  ][    main][     ValidationUtils:761] SUCCESS: NTP servers on machine verified successfully
2015-07-01 12:31:03,713 [INFO  ][    main][     ValidationUtils:761] SUCCESS: NTP servers on machine verified successfully
2015-07-01 12:31:03,714 [INFO  ][    main][     ValidationUtils:778] Following errors were found...
2015-07-01 12:31:03,714 [INFO  ][     (more...)

HAIP and Exadata

If you’ve run an exachk report, y0u may have seen the following message with regard to your databases:

Status Type Message Status On Details
FAIL Database Check Database parameter CLUSTER_INTERCONNECTS is NOT set to the recommended value db01:dbm011, db02:dbm012 View

This check is commonly seen when a database is created on Exadata without using the custom “Exadata” templates included with the database creation assistant.  These customized templates include a multitude of recommended parameter settings found in (more...)

MGMTDB not automatically created on Exadata X5 and GI

While deploying an X5 Full Rack recently it happened that the Grid Infrastructure Management Repository was not created by onecommand. The GIMR database was optional in and became mandatory in and should be automatically installed with Oracle Grid Infrastructure 12c release 1 ( For unknown reason to me that didn’t happen and I had to create it manually. I’ve checked all the log files (more...)

Investigating the full table direct path / buffered decision.

A lot of blogposts and other internet publications have been written on the full segment scan behaviour of a serial process starting from Oracle version 11gR2. This behaviour is the Oracle engine making a decision between scanning the blocks of a segment into the Oracle buffercache or scanning these blocks into the process’ private process global area (PGA). This decision is even more important on the Exadata platform, because the Oracle engine must have made (more...) post upgrade step fails on Exadata storage software

I’ve done several Exadata deployments in the past two months and had to upgrade the Exadata storage software on half of them. Reason for that was because units shipped before May had their Exadata storage software version of

The upgrade process of the database nodes ran fine but when I ran -c for completing post upgrade steps I got an error that the system wasn’t on the expected (more...)

A Deep Dive into ASM redundancy in Exadata

I made this presentation at Serbia Oracle User Group event in Zlatibor and Harmony 2015 event in Tallinn at last month. Both were very nice organizations that i really enjoyed, learned much and met with many Oracle experts. I prepared this presentation to answer to following questions, which i think are really important for Exadata Database Machine administrators: - To what degree, disk and

How do I change DNS servers on Exadata storage servers

This is just a quick post to highlight a problem I had recently on another Exadata deployment.

For the most customers the management network on Exadata is routable and the DNS servers are accessible. However in a recent deployment for a financial organization this wasn’t the case and the storage servers were NOT able to reach the DNS servers. The customer provided a different set of DNS servers within the management network which were still (more...)

How to configure Power Distribution Units on Exadata X5

I’ve done several Exadata deployments recently and I have to say of all the components PDUs were hardest to configure. Important to notice that unlike earlier generations of Exadata the PDUs in X5 are Ehnanced PDUs and not Standard.

Reading the public documentation (Configuring the Power Distribution Units) it says that on PDUs with three power input leads you need to connect the middle power lead to the power source. Well I’ve done (more...)

IO Resource Manager for Pluggable Databases in Exadata

Another interesting topic that goes over and above the CDB Resource Manager Plans I described earlier this week is the implementation of IORM Plans for Pluggable Databases. Pluggable Databases are an interesting object for studies, and I like to research things. When 12c came out there was no support for offloading initially, it is required that you are on cell software 12.1.x.x.x for full 12c support on Exadata. One aspect I was particularly (more...)

Testing 12c CDB Resource Plans and a little bit about OEM Express

Inspired by Sue Lee’s presentation at Enkitec’s E4 conference I decided to re-run my test suite to work out how you can use Database and I/O Resource Manager in Oracle to help consolidating databases in the new Multi-Tenant architecture. I should point out briefly that the use of Multi-Tenant as demonstrated in this article requires you to have a license. Tuning tools shown will also require you to be appropriately (more...)

Smart Scan enhancements in Oracle Exadata 12c-inline LOBs

As part of the 12c release of the database and cellos Oracle introduced the ability to perform Smart Scans on inline LOBs. The enhancement is certainly for Secure Files only. And as always, if you would like to read up about Secure Files you can head over to Tim Hall’s website for the details.

To demonstrate the new behaviour I have used an BP 22 database on Exadata 11.2.3. (more...) fails with Unable to locate any IB switches

With the release of Exadata X5 Oracle introduced elastic configurations and changed the process on how the initial configuration is performed. Back before you had to run which would go across the nodes and change all the settings according to your config. This script has now evolved and it’s called which is part of OEDA (onecommand). During one of the recent deployments I ran into the below problem:

[root@node8 linux-x64]# ./applyElasticConfig. (more...)

How to configure Link Aggregation Control Protocol on Exadata

During a recent X5 installation I had to configure Link Aggregation Control Protocol (LACP) on the client network of the compute nodes. Although the ports were running at 10Gbits and default configuration of Active/Passive works perfectly fine the customer wanted even distribution of traffic and workload across their core switches.

Link Aggregation Control Protocol (LACP), also known as 802.3ad is a methods of combining multiple physical network connections into one logical connection to increase (more...)

Exadata Fast Data File Creation

This post is the result of some testing I performed on Exadata data file creation. You may know that Exadata offloading incorporates SQL optimisations as well as some infrastructure work. For quite some time Exadata allowed the DBA to create data files a lot quicker than on traditional systems. This has been documented before, for example by @mpnsh here

The final comment on his blog entry was a remark that data file creation is quite (more...)