Weekend Learning: Background information on using 4k redo logs on Flash and SSD-based storage devices

Check out MOS document "Using 4k Redo Logs on Flash and SSD-based Storage" from note 1681266.1 to get details about using 4k storage media like Flash and SSD to see how they can be logically setup or used in hybrid situations to avoid misaligned I/O issues!

Exadata: CellCLI "list activerequest" command can produce I/O hang in Storage Server

Do not miss out on applying the patch to resolve the issue described in the MOS article "(EX27) Database IO may hang when CellCLI command "list activerequest" is executed on an Exadata Storage Server" from note ID 2095255.1 so your system is not subject to this if you ever need to run the command in an Exadata machine!

Exadata: InfiniBand may fail to send messages to cause I/O failures on Oracle VM

If you are running Exadata on Oracle VM, you need to look at the article "(EX26) Messages over the InfiniBand network may fail to send causing IO failures and hangs when using Exadata OVM with Exadata cell version 12.1.2.1.3" in My Oracle Support from note ID 2105407.1 as there is a pretty straightforward way to resolve this, even if it might not be the kind of solution you are looking for!

12c: CRS processes restart periodically on cluster nodes

From MOS note ID 2074515.1 we find the article "CRS Processes Periodically Restart In Some Cluster Nodes in 12.1.0.2" which may be very important to keep an eye out for this showing up in your alert/trace files because it is caused by several slow ASM I/Os in a row!

Oracle Cloud: DaaS customers need to patch due to excessive I/O

Tonight we get an article from MOS entitled "ALERT: Customers with Database as a Service instances must apply a critical patch as soon as possible" from document ID 2068023.1 which is important because specific disk volumes can grow to 90%, prevent backups from running, and a negative I/O performance issue can occur!

Unable to communicate with ASM mirror copy if Exadata Storage Server is offline

Tonight the MOS document "(DB32) Bug 20217875 - When using normal redundancy Oracle is unable to perform I/O to an ASM mirror copy when an Exadata Storage Server is offline" from note 2057731.1 seems straightforward BUT shows how complicated ASM and Storage Servers are with even more reasons to be constantly monitoring these components!

Exadata: New feature Exadata I/O Latency Capping causing ORA-27626 errors

Tonight we find out in My Oracle Support document 1925661.1 "ORA-27626: Exadata error : 2201 (IO cancelled due to slow/hung disk)" that the new feature Exadata I/O Latency Capping introduced with Exadata Storage Server 11.2.3.3.1 can actually interfere with I/O reads so learn what error messages you can prepare for in the log and trace files!

Exadata: DB/ASM I/O request hangs if one cell has a problem

Very similar to my post on LCK0 hanging, there is a specific slant to the My Oracle Support document "Exadata Database Or ASM Instance Hung On IO Request When Single Cell Is Having Problem" via note ID 2002084.1 is worth checking out because there are some log entries we can look for to alert us about the next time we have this problem PLUS there is the bug that we can patch our system with too to prevent it!

Exadata: Synchronous I/O can cause disk corruption

Sure you might be saying to yourself, most I/O operations for Exadata are asynchronous and this only affects versions 12.1.1.1.2 and 12.1.2.1.1 of the Storage Server software so why is this a big deal?  Do you know for sure you will not be upgrading to one of these versions of software?  Do you think these versions are the only versions where this bug will crop up?  Does this make you wonder how to monitor your disks for this kind of thing?  Well the good news is that you can visit My Oracle Support document "Bug 20830449 - Disk corruption possible when a disk media error occurs while synchronous I/O is performed" for note ID 2009841.1 to find out which version of software has a patch available, and which one does not have the patch yet at this time!

Getting to know issues with 'read by other session' wait event

Do you like adding tools to your toolbox?  Have you been in a situation where you needed to research the wait even that a session is just sitting in?  Then tonight the article "Resolving Issues Where 'read by other session' Waits Occur When I/O is NOT Slow and Cause is Unknown" from MOS note ID 1476081.1 is probably exactly what you are looking for to add a little something to your arsenal!

Weekend Learning: Slow database I/O

If you've always wondered about your database I/O performance, ways to measure and interpret it, or some documentation on the subject you're in luck today!  I found the article "How to Tell if the I/O of the Database is Slow" on My Oracle Support under note 1275596.1 and it starts to help peel back the onion of performance a bit, especially with all the documents linked within the note, so I saved it knowing this was something I wanted to review in depth when I had some time.  I suggest if you're interested in performance on an Oracle system, you do the same this weekend with me.  Maybe we'll compare notes at the end with a quiz.  :}