12c: Updates to Fast-Refresh Materialized Views with joins are lost after DB upgrade

An interesting article on My Oracle Support, "Updates Lost to Fast-Refresh Materialized Views with Joins After Upgrade to 12c" from document ID 2186836.1, tells us that an upgrade from 12.1.0.1 to 12.1.0.2 can negatively impact your fast-refresh materialized views with joins!  It seems that the system "covers up" the problem by having the last update date updated while the data does not get updated!!

12c: KGLH0 process is causing Shared Pool ORA-04031 errors and latch contention

Are you looking to upgrade your Oracle database to 12.1.0.2 soon?  You might want to read "Bug 20370037 - Shared Pool from KGLH0 constantly growing causing ORA-04031 and Latch contention" from MOS note 2119923.1 because there seems to be several well known bugs with the KGLH0 process and this document has steps for different ways to mitigate this.  What does that mean?  If there are a lot of ways to encounter this in the system, then you need to prepare for encountering it so deploy the upgrade in QA and stress test to see if you run into this!!

Exadata: Flash Cache Compression on X3 and X4 Storage Servers causing disk drive failures

Check what version of software you have on your Storage Servers immediately due to the bug listed in "(EX28) High risk of data loss on X3 or X4 Exadata storage when flash compression is enabled and running late 2015 or early 2016 software release" MOS article ID 2115005.1 which currently has NO solution!  There is a workaround listed, but that is turning off the Flash Cache Compression which will likely negatively affect the performance of your Exadata application and Oracle gives some great advice about proceeding with caution if you are planning upgrading!

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!

11gR2: ASH report has "null event" wait event

The My Oracle Support article "'Null Event' Wait Events Occurs Intermittently in ASH Report" from document ID 2102027.1 clues us into a known bug which is resolved in 12.2 and lets us know that this is a pretty insignificant issue but it is really important to know this does not mean anything so we do not freak out when we see it in the wild!

Weekend Learning: Creating statistics on global temporary tables

While the note "How to Create Statistics on Global Temporary Tables" on My Oracle Support from article ID 351190.1 is talking about post 9.2.0.6 Oracle databases, it also has specific information on how this is different for 12c and introduces the idea of dynamic sampling as well!  How does this apply to you?  Well, I have seen system generated global temporary tables perform badly where you really do not have any control over it, so this could possibly give you some kind of control!

Windows: 12c forms instance does not exist after startup

Are you running 12c on Windows?  We don't really run on Windows, but MOS document "Forms 12c Instance (FORMS_INSTANCE) "forms1" and Forms Related Registry Variables Do not Exist after Starting Nodemanager and Adminserver" via note ID 2094031.1 taught me something new tonight about the folder structure and what the solution is for this problem so maybe someday I can use it!

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!

12c: Error ORA-01467 received when using Extended Data Types

With a bug still being worked on by development, there is a workaround listed in MOS document "ORA-01467 In Oracle 12c when max_string_size is Extended Data Types used" via note ID 2022269.1 with a way to convert your query so the sort path is reduced.  If Extended Data Types for 12c is new to you, this would be a great time to learn and find out what My Oracle Support can tell you about the feature!

ASM: After disk comes online resync takes excessive amount of time

If you want to learn a bit more about ASM, especially if you have Exadata because it is affected as well, check out MOS article "ASM disk resync takes long time after disk online" from document ID 2061405.1 including the object GV$ASM_OPERATION which if you investigate on your system maybe you could develop alerts based on it!

ALERT: DB corruption after 12c upgrade for compressed tables during recovery

Did you compress tables on 11g before going to 12c?  If so, you need to check out My Oracle Support article "ALERT Bug 21682261 Corruption during Recovery after upgrading to 12c for Compressed Tables" from document ID 2058461.1 because you can run into corrupted tables if you need to recover them!  This is the worst possible news for a database because it violates all of the ACID principles and if you get to the recovery stage you already have your data in question!

12c: DB 12.1.0.2 patch 12 known issues

Did you know that the latest patch for 12.1.0.2 has known issues already?  While article "Oracle Quarterly Database Patch 12.1.0.2.12 Known Issues" found on My Oracle Support by document ID 2052715.1 has a very small issue, it makes me curious going forward about how we find these known issues bug reports in the future for other DB patches as well!

Patches for SQL Plan Management issues

Did you know there are patches which you can apply to limit potential problems with SQL Plan Management?  Check out MOS note 2035898.1 for the document "Patches to Consider for 12.1.0.2 to Avoid Problems with SQL Plan Management (SPM)" which is directed at 12c, but has links for patches that can be applied to 11gR2 as well!

Weekend Learning: Upgrading to Oracle Database 12c R1 using DB Upgrade Assistant

Of course I, and this blog, am focused on applications and Support/Operation of those applications, but sometimes we need to step into the shoes of our DBAs to learn something new which we can later apply to our discipline!  MOS document "Complete Checklist for Upgrading to Oracle Database 12c Release 1 using DBUA" is that kind of knowledge which you can find via article ID 1516557.1 to get some more details about files, objects, and other steps/scripts which you could find useful down the road!

R12 Payables: Payment Exception Report returns no data after 12c DB upgrade

Note 2029537.1 on My Oracle Support for article "R12:AP Payment Exception Report Does Not Retrieve Data After Database Upgrade to Version 12c" reminds us that any type of change we introduce into our systems is reason enough to run through our testing suites to validate each and every piece of the application because any change can cause problems for us!

12.1.0.2: Upgrade failing due to edition problems

While the MOS article "Database Upgrade to 12.1.0.2 Fails with Error: “ORA-38802: edition does not exist”" has a pretty clear title, note ID 1995415.1 does not have a whole lot of details beyond the bug and that there is a patch associated to fixing this.  Well looking at the bug has the details we are looking for since it seems like several objects, especially ORA$BASE, have no edition information so the installer is crashing!

Weekend Learning: 12c: Automatic Dynamic Statistics

Did you know that Oracle Database 12.1 introduces some new ways to sample dynamic statistics for query optimization?  You are probably familiar with setting this in the 11gR2 world but 12c allows us to set this at a more granular level so it can be done at a statement level and you can find all the details at "Automatic Dynamic Statistics" on My Oracle Support from note ID 2002108.1 to see what has to be enabled for this to work.

12c: High memory and CPU usage with ocssd.bin

The My Oracle Support document "12c ocssd.bin high memory/CPU usage" via note ID 1965082.1 has shown up several times on the list of recently updated articles, so I figure tonight is a good time to make sure everybody is seeing this.  Make sure you apply this patch to prevent the 8MB an hour memory leak, and then investigate the other issues reported here on the AIX platform!

Leap seconds, Exadata, Oracle DB and Linux OS

Are you aware we are having a leap second added at the end of June?  Do you know how that affects Exadata?  Refer to My Oracle Support document "Leap Second Time Adjustment (e.g. on June 30, 2015 at 23:59:59 UTC) and Its Impact on Exadata Database Machine" from article ID 1986986.1 to find out why you need to be worried about it if you have upgraded any infrastructure to the 12.1.2.1.0 version of software but you do not need to be worried if you have any other version of Exadata software installed.

Do you just want to know more about what a leap second is, and how it affects an Oracle DB?  Then MOS article "Leap seconds (extra second in a year) and impact on the Oracle database." from note ID 730795.1 will be your cup of tea while article "How Leap Second Affects The OS Clock on Linux and Oracle VM" from document ID 1453523.1 clues you in on how the Linux OS could be affected with or without the ntp service being installed on your system.