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?
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...)
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
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 18.104.22.168 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...)
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
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...)
Happy New Year! Upgraded 22.214.171.124 Grid Infrastructure to 126.96.36.199 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 […]
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...)
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
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...)
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 188.8.131.52!).
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...)
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...)
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...)
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 184.108.40.206 BP16 to 220.127.116.11 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...)
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 groupContext:
This research stems from a recent case I have investigated where the data disk group of a test (more...)
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...)
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...)
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...)
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
asmcmd rm -f +TEMP/db112/temp_01. (more...)