Resolving ORA-27090: Unable to reserve kernel resources for asynchronous disk I/O in Oracle 12c

I have been running into some problems recently with 12cR2 databases and Kevin Clossons’ SLOB tool.

The SLOB script allows for the concurrent loading of multiple schemas, and if you are loading a large amount of data, being able to load concurrently is a significant time saver.

With LOAD_PARALLEL_DEGREE set to 8, I got the following error:

ORA-27090: Unable to reserve kernel resources for asynchronous disk I/O
Linux-x86_64 Error: 11: Resource temporarily unavailable
Additional information: 3
Additional information: 128
Additional information: 140728056780720

These servers were new Dell R630s with plenty of horsepower, so the idea that just 8 parallel threads would cause this type of a failure was puzzling.

Further investigation of the trace file showed that the problem occured on the index shrink command:

ERROR at line 1:
ORA-12801: error signaled in parallel query server P13L, instance
sio04-mgmt.asp.lab.mcl:slob4 (4)

After some time investigating, it seems Oracle 12c has a much higher target for PARALLEL_MAX_SERVERS and PARALLEL_SERVERS_TARGET.  In my case, PARALLEL_MAX_SERVERS had defaulted to 2240.

Since the SLOB data load uses the parallel query option, Oracle was spawning thousands of slave processes all trying to issue ASYNC IO.

So I set the numbers to what I considered more reasonable:

SQL> alter system set parallel_max_servers=400 sid='*';

System altered.

SQL> alter system set parallel_min_servers=40 sid='*';

System altered.

SQL> alter system set parallel_servers_target=400 sid='*';

System altered.

Now SLOB was able to load data with eight concurrent processes.

Adding VVols to vCenter from a Dell EMC Unity all flash array

The Dell EMC Unity array is a capable mid-market platform able to support a variety of workloads.

In the all-flash configuration it delivers good performance for Oracle databases, and with the ability to support VVols is a good choice for databases virtualized with VMware ESX 6.

The following blog post walks you through adding VVol based shared storage for an Oracle 12c RAC using ASM and virtualized on VMware ESX 6.

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UDEV rules for ASM disks on RHEL7

On this blog and elsewhere you will find UDEV rules examples for setting device ownership and naming consistency on older versions of Linux.

With RHEL7 some of the syntax has changed slightly.

This example was created using OEL7 with the Red Hat kernel, but should also work on Red Hat and CentOS.

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Oracle User Profiles; Verifying and Changing the default profile

This is an issue that keeps tripping me up in the development lab.

I create a quick database, and then after some time I go back to try to log in, and get:

ORA-28002: the password will expire within 7 days

And then I spend a while trying to figure out how to disable the password expiry component of the profile.

Here then, for my benefit as much as anyone else, is my quick guide to checking the user profile, and then disabling security components that cause headaches in the development lab.

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IPO announced? Be sure your Oracle licenses are in order…

I have stated this before. I am not a lawyer.

Neither am I an investment expert. Heck I ploughed money into Transocean two months before the Deepwater Horizon sank to the bottom of the Gulf and left a destructive oily mess all over the Gulf Coast.

So don’t take any stock picks from me.

But on a recent trip to the Midwest I met with a customer in an interesting predicament.

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