I am not sure how this situation arises, but I discovered that sometimes the windows installer (Puppet based) on Windows gets into a state where it isn’t installed, but thinks it is, which means that the install won’t work, but it generates messages as if it had worked.

Under c:\psft\pt\ps_home8.55.23 is only the jre directory. Running the install again appears to work, but doesn’t do anything.

The solution is to run the uninstall, then the install will work.

I got an error from powershell:

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PS C:\> Start-Process -NoNewWindow -Verb RunAs
Start-Process : Parameter set cannot be resolved using the specified named
parameters.
At line:1 char:1
+ start-process -NoNewWindow -verb runas
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Start-Process], ParameterB
   indingException
    + FullyQualifiedErrorId : AmbiguousParameterSet,Microsoft.PowerShell.Comma
   nds.StartProcessCommand

This is because the Start-Process command has two parameter sets. Looking at the page linked, the parameters are listed in two groups. These groups can’t be mixed and matched. You have to pick one or the other. So if you want to do runas, you can’t use NoNewWindow.

A nice feature of RMAN is that if a restore fails, and you rerun it, it realises that it doesn’t have to redo all the work it has already done.

At least, that is usually what happens.

Today we got:

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RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of Duplicate Db command at 03/29/2018 12:54:29
RMAN-05501: aborting duplication of target database
RMAN-03015: error occurred in stored script Memory Script
RMAN-06004: ORACLE error from recovery catalog database:
    RMAN-20003: target database incarnation not found in recovery catalog

As documented in oracle support note 2036644.1, this is caused by oracle bug 14683854, and the workaround is to remove

I have been thinking about our DR process, and how to improve it. More on that in a later post. However we recently had a couple of planned server room outages, where my previous planning has been beneficial.

Production is redundant and resilient across our server rooms. However, the other environments are not because redundancy is expensive and only really needed for production systems.

So what we do is to have half of the non-production systems at one site. and the other half at the other. This means that we can shut a machine room down, and half the development environments will continue to run.

Here is another issue we had with RMAN. This one has been bugging me for years.

We were doing a duplicate using rman. For some reason the recovery catalogue didn’t contain the archive log we needed to do the recovery, so the restore completed, and finished with the familiar error:

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...
executing command: SET until clause

Starting recover at 2018-02-02 16:03:13

starting media recovery

unable to find archived log
archived log thread=1 sequence=307
Oracle Error:
ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01152: file 1 was not restored from a sufficiently old backup
ORA-01110: data file 1: 'system.dbf'

The normal thing to do here is to correct the error, and redo the backup. But we already had the redo logs on the disc, and wanted to be able to apply them.

Different Scenarios

In my previous post on this topic, I noted that you could use the snapshot time on the recover database command to recover the database from a SAN snapshot.

I realise that there are different possible scenarios and my write up wasn’t clear on which approach is applicable when. Also, the test I did was unrealistic as I used the logs after the snapshot was taken, and the whole point of using SAN snapshots is that they contain everything required for a crash consistent recovery.

Lots of people seem to like Oracles Recovery manager. I am not one of them. I think this is because of a lack of understanding on my part of how it works. It is a complex beast, and at the same time has some annoying limitations.

I like to automate things. I have a number of scripts to call RMAN to do backups and restores in common situations. These fail far too often for my liking. I feel I should look into why. Maybe I can learn to love RMAN? We shall see.

We are running a data conversion and got a wait event I don’t normally see: The brown is identified as Configuration. It I drill down, I can see more detail. Here light purple is HW Contention (i.e. High Watermark Contention). Darker purple is Write Complete waits, and yellow is buffer busy waits.

We have deferred segment creation switched on for the database. This means that the segment needs to be created before data can be written. The high watermark can only be moved by one process at a time.