Brief introduction to ASM mirroring

Automatic Storage Management (ASM) is becoming the standard for good reasons. Still, the way it mirrors remains a mystery for many customers I encounter, so I decided to cover it briefly here.

ASM Basics: What does normal redundancy mean at all?

ASM normal redundancy

It means that every stripe is mirrored once. There is a primary on one disk and a mirror on another disk. All stripes are spread across all disks. High redundancy would mean that every (more...)

Primary on FileSystem and Standby on ASM

For one of the client, standby server went down. We had another standby server which was kept down for more than a month. Decision was taken to start the server and apply incremental SCN based backup on the standby database.

The standby was on ASM and the Primary on filesystem.Incremental backup was started from the SCN reported by below query

select min(fhscn) from x$kcvfh;

Once the backup completed, it was transferred to standby, standby (more...)

Stopping one ASM listener in Flex ASM environment takes down ASM instance

Stopping one ASM listener in Flex ASM environment takes down ASM instance

This is a heads-up about behaviour we are seeing during OAT testing on a 12c environment. We are running OAT tests on a new 12.1.0.2 Grid Infrastructure environment using Flex ASM (OEL 5.8) and when taking down one of the two ASMNETLSNR listeners on one of the nodes, the ASM instance running on that node is taken down. We (more...)

My bizarre question of 2015 already

To be honest it was asked 2 years ago in a blog about ASM and rebalancing and someone asked the following question

Can I upgrade ASM from 10205 to 11203 while ASM rebalancing is in progress?
and the answer, unsurprisingly, was
No.
Why would anyone even think of asking that question never mind contemplating the idea of running an upgrade under such circumstances.
Needless to say my next blog post is about ASM related activities (more...)

Install and Upgrade Grid Infrastructure 12.1.0.2

Happy New Year! Upgraded 12.1.0.1 Grid Infrastructure to 12.1.0.2 and applied the Oct 2014 PSU. Had an error during rootupgrade.sh as well, due to the ASM spfile being on disk instead of on ASM diskgroup (MOS Note: Upgrading ASM Failed With ORA-32002: cannot create SPFILE – Doc ID 1912581.1). The install & upgrade steps documented […]

Mount ASM diskgroups with new ASM instance

Imagine you have 11gR2 Oracle Restart configuration with database files located in ASM.

After server crash you realized that local disks are corrupted and with local disks you lost all Oracle installations. Even though this is important system you don’t have database backup (always take backups!).

But you managed to save all ASM disks as they were located on separate storage.


This will be small beginner guide on how to help yourself in such (more...)

No Write Permission on ACFS Mount Point



Last night, I managed to create the ACFS Mount Point after resolving the issue "ACFS-9459: ASVM/ACFS is not supported on this os version". But, after creating the ACFS Mount Point, I'm unable to create or touch any files under this ACFS Mount Point.

Though, I tried to touch a file to create files under this ACFS Mount Point using OS User Oracle and Root, it's failing with the following error:

"touch: cannot touch `x': (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

Using Oracle Flex ASM with single instance database

Oracle Flex ASM was introduced in 12c version. This is one of the best features introduced with new version in my opinion.

I won’t speak in detail about Flex ASM because you can find more information in documentation. In this post I will concentrate on how Flex ASM handles crash of ASM instance.

For this test I’ve created 2 node cluster - 12c Grid Infrastructure with Flex ASM enabled.


$ asmcmd showclustermode
ASM cluster : (more...)

ASM Startup Fails With ORA-04031 After Adding CPUs

A few weeks ago we upgraded one of our production server, adding another CPU tray. This brought the number of CPU cores from 80 to 160, and took us from 2Tb of RAM to 4Tb (just in time for Oracle to announce the in-memory database in 12.1.0.2!).

However when I went to start things up, ASM wasn't starting up, giving me these errors:

ORA-04031: unable to allocate 32 bytes of shared (more...)

ASM Metadata, Internals and Diagnostic Utilities

If you use ASM on a regular basis, you may find that knowledge of the internals can be very useful for advanced troubleshooting and in general to acquire familiarity with the technology. In particular this is even more relevant when using ASM capabilities for data redundancy/mirroring (i.e. when deploying disk groups with normal or high redundancy).

I have first started investigating this topic when deploying 10g RAC databases in 2005. From time to time (more...)

Oracle ASM 12c: New Features

Last week I was lucky enough to be presenting at the UKOUG AIM SIG. There was a decent enough crowd in attendance and there were some really interesting talks and some really good speakers. In particularly I found Chris Lawless speaking on replication a particularly engaging speaker, and Dave Webster really held the audiences attention late in day.

I was giving a presentation on the new features available to you with 12c ASM. The presentation (more...)

Working Around an ASM Startup Problem

Scenario

I recently hit the problem covered in MOS note “ASM Instance Is Not Coming Up ORA-00064 (1,4468736,Kfchl Array) Kfchl Array (Doc ID 1328620.1)” mid-way through a Grid Infrastructure upgrade from 11.2.0.2 BP16 to 11.2.0.4 BP3 on Exadata. Specifically, it was the application of prerequisite patch 17783101 (required for downgrades) to node 3 that hit the problem. At this point nodes 1 and 2 had been successfully patched (more...)

Bug 18223021 : DISK FILE OPERATIONS I/O ON HP-UX.

We have been dealing with a strange ASM  behavior over the past few months across all ASM instances in our multiple Oracle 11gR2 (11.2.0.2) Cluster envs on HPUX 11.31 OS. Even a simple and typical ASM task like, adding new disk to ASM disk group, disk group mount/unmount and querying for CANDIDATE asm disks was taking min of 20 minutes, and sometimes infinity time. This behavior caused a lot of performance (more...)

How to Recover Files from a Dropped ASM Disk Group

Topic: This post describes a few tips and techniques on how to recover ASM files from a dropped disk group and an example of how to 'undrop' an ASM disk group

Context: This research stems from a recent case I have investigated where the data disk group of a test (more...)

Openfiler on Virtualbox and 12c Oracle Flex ASM

Original Post can be viewed at Openfiler on Virtualbox and 12c Oracle Flex ASM

Last week Oracle released 12c database and Oracle blogosphere is bustling with lot of people posting details about new versions and setup. I too decided to take plunge and setup my own RAC cluster. I had (more...)

ASM AU Size And LMT AUTOALLOCATE

When using Locally Managed Tablespaces (LMT) with variable, system managed extent sizes (AUTOALLOCATE) and data files residing in ASM the Allocation Unit (AU) size can make a significant difference to the algorithm that searches for free extents.The corresponding free extent search algorithm when searching for free extents >= the AU size seems to only search for free extents on AU boundaries in order to avoid I/O splitting.Furthermore the algorithm seems to (more...)

Physical vs Logical Blocksize on ASMLib Devices

As you all may know, ASMLib is a recommended module for Oracle databases running on Linux platforms and it is an embedded module for UEK (Oracle Unbreakable Kernel) users. Oracle announced that (two years ago or so) they will no longer maintain ASMLib for Red Hat compatible kernel but this does not mean that they abandon the project, rather it is mainly related to the effort they need to put in maintaining the module for multiple kernel versions.

A while ago, Oracle added a new feature to ASMLib allowing ASM devices to choose between physical or logical block sizes in (more...)

¿Cómo mover ocr y vdisk a nuevo disk array?

No hace mucho, uno de mis clientes inició el proceso de migración de su disk storage system, desde EMC CX4 hacia EMC VNX. Ellos tienen sus bases de datos operando con Oracle RAC 11.2.0.3, por lo que siguieron el procedimiento de agregar LUNs del nuevo EMC VNX en los diskgroups de datos, para luego retirar los LUNs del antiguo EMC CX4, aprovechando el rebalanceo automático que hace ASM al agregarle y (more...)

asmcmd non-interactive commands in MS-DOS Batches

In the last days I was fighting with a nice behaviour of the asmcmd non-interactive mode in MS-DOS batches.

I wanted to delete several files located in ASM within a MS-DOS batch:

REM Script: asm_cleanup_DB112.cmd
set ORACLE_BASE=E:\oracle
set ORACLE_HOME=E:\oracle\product\grid-11.2.0
set ORACLE_SID=+ASM
set PATH=%ORACLE_HOME%\bin;%PATH%
asmcmd rm -f +TEMP/db112/temp_01. (more...)