min/max Upgrade

A question came up on the OTN database forum a little while ago about a very simple query that was taking different execution paths on two databases with the same table and index definitions and similar data. In one database the plan used the “index full scan (min/max)” operation while the other database used a brute force “index fast full scan” operation.

In most circumstances the starting point to address a question like this is (more...)


One of the difficulties with trouble-shooting is that’s it very easy to overlook, or forget to go hunting for, the little details that turn a puzzle into a simple problem. Here’s an example showing how you can read a bit of an AWR report and think you’ve found an unpleasant anomaly. I’ve created a little model and taken a couple of AWR snapshots a few seconds apart so the numbers involved are going to be (more...)

Quiz Night

The following is a straight, continuous, untouched, cut-n-paste from an SQL*Plus session on How come the update doesn’t execute in parallel – noting that parallel DML has been enabled and the tablescan to identify rows to be updated does execute in parallel ?

SQL> desc t1
 Name                                                                            Null?    Type
 ------------------------------------------------------------------------------- -------- ------------------------------------------------------
 OWNER                                                                           NOT NULL VARCHAR2(128)
 OBJECT_NAME                                                                     NOT NULL VARCHAR2(128)
 SUBOBJECT_NAME                                                                           VARCHAR2(128)
 OBJECT_ID                                                                       NOT NULL NUMBER
 DATA_OBJECT_ID                                                                           NUMBER
 OBJECT_TYPE                                                                              VARCHAR2(23)
 CREATED                                                                         NOT  (more...)

How to speed up slow unicode migration of a table with xmltype columns

Recently I have had an issue with slow unicode migration of the database upgraded from 10g to The main problem was a table with xmltype: we spent about 4 hours for this table(~17GB) during test migration, though all other tables (~190GB) migrated just for about 20 minutes.
We used DMU(Database Migration Assistant for Unicode), and the root cause of the problem was update statement generated by DMU for this table:

update   (more...)

Exadata Cell Patching – USB I/O Errors

I was playing around with the Exadata X2-2 in the Enkitec lab this weekend, and hit an interesting issue when patching the storage servers.  We were taking the system up to version for testing purposes.  I fired off the patchmgr script, and one of the storage servers failed when beginning the first phase of the patching cycle:

[root@enkdb03 patch_12.]# ./patchmgr -cells cell_group -patch -ignore_alerts

Scanning an Index

The internet is full of information about indexes, and for a reason. Indexes in a database is probably the most important performance related topic. There are so many cases, properties, and different ways to use indexes that there is simply a lot to write about. In this post I’d like to talk about a specific … Continue reading Scanning an Index

Reduce Hard Parse time using SQL Profile

Few days ago we had concurrency problem with "cursor: pin S wait on X" wait event. This wait event is mostly associated with parsing in some form.

After quick diagnosis I’ve found problematic query. It was fairly complex query which was executed very often with average 0.20 seconds of execution time. As this query was using bind variables, Oracle reused existing plan and problems with "cursor: pin S wait on X" wait (more...)

ORA-38301: can not perform DDL/DML over objects in Recycle Bin

           While dropping a tablespace, getting error ORA-38301: can not perform DDL/DML over objects in Recycle Bin .

SQL> drop tablespace DATA including contents and datafiles;
drop tablespace DATA including contents and datafiles
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-38301: can not perform DDL/DML over objects in Recycle Bin



Before dropping the tablespace, disable recyclbin . 

1. Disable recyclebin:

SQL> ALTER SYSTEM SET recyclebin (more...)

RMAN-20005: target database name is ambiguous

                          While running rman commands from the catalog database, you might get the error RMAN-20005: target database name is ambiguous. , if the database was restored from another database.


rman target sys/oracle#51234@RMANBKP catalog rman_b2ccrmpd/rman@catdb

Recovery Manager: Release – Production on Fri Oct 14 10:34:05 2016

Copyright (c) 1982, 2014, Oracle and/or its affiliates. All rights reserved.

connected to (more...)

Hit by the ‘Tech Support’ Scammers

I got a call earlier today from the Tech Support Scammers. You’ve probably heard of this horribly unethical practice already, but the premise is that they cold-call seemingly randomly and try to convince you that there is a problem with your PC/router, and then attempt to get you to allow them remote access to your PC to ‘fix it’. Some then claim problems are due to expired warranties on the computer and demand payment, others (more...)

Slow full table scan due to row chaining

Few days ago I’ve received complaint that simple count on 2 million rows table is running forever.

This was the statement:

select count(1)
from CLIENT k
where k.expires is null;

I've used fake names for table name and columns.
Database version:

Indeed, query was running longer than I would expect. Oracle was using FULL SCAN of the table with "db file sequential read" wait events. This was little odd (more...)

Extended Stack Profiling – Ideas, Tools and Comments

Topic: This post provides a short summary and pointers to previous work on Extended Stack Profiling for troubleshooting and performance investigations.

Understanding the workload is an important part of troubleshooting activities. We seek answers to questions like: what is the system doing, where is the time spent, which code paths are most used, what are the wait events, etc. Sometimes the relevant diagnostic data is easy to find, other times we need to dig (more...)

Analyze database activity using v$log_history

The v$log_history view contains important information on how application’s users use the database , this view can help you define periods with the most activity in the database. v$log_history queries You can adapt the query to your needs, you just have to change the way you format the date to be able to drilldown to the … Continue reading Analyze database activity using v$log_history

The post Analyze database activity using v$log_history appeared first on Oracle (more...)

MRP process on standby stops with ORA-00600

A rather not so great post about an ORA-00600 error i faced on a standby database. Environement was on Sun Super Cluster machine. MRP process was hitting ORA-00600 while trying to apply a specific archive log.

The error message was something like this

MRP0: Background Media Recovery terminated with error 600
Errors in file /u01/app/oracle/product/
ORA-00600: internal error code, arguments: [2619], [539], [], [], [], [], [],  (more...)

ORA-19599 block corruption when filesystemio_options=SETALL on ext4 file system using Linux

Few days ago I experienced strange issue in my development environment running on OEL 5.8 with EXT4 filesystem. Note - EXT4 filesystem is supported from OEL 5.6 version.

This was virtual machine running oldish Oracle database.

I noticed that backup for my database is failing because of archive log corruption. As this is development database I've simply deleted corrupted archive logs and initiated full backup again. But backup (more...)

PeopleTools 8.54 Feature: Application Engine Trace File Enhancements

In this blog, we have been reviewing the new features of PeopleTools 8.54. Today is the turn of Application Engine, particularly on its troubleshooting. This release of PeopleTools include several enhancements on Application Engine tracing, which are outlined below:

  • The .AET trace file can now include the PeopleCode trace. This removes the need of checking the .AET file for the the non-PeopleCode steps and the .TRC file for the PeopleCode steps. Surely, .TRC files (more...)

Being Right and Proving It

One of the great things about working in IT is that you can often win an argument simply by being right. Not because of who you are or because you are more eloquent than others, but because the facts support your position. Almost every IT person I have ever met respects facts.

In order to win arguments this way, you of course need some facts to work with. And that’s where too many people fail. (more...)

Debugging Faulty Assumptions

I wanted to install Oracle JDevelper 12.1.3 – a version that I had been eagerly awaiting. Since my primary machine is a MacBook, I wanted to install it on OS X 10.9.3.

I downloaded the generic installer and found that the install didn’t run. Since OS X had disappeared from the documentation, I assumed that I would have to fiddle around until I found a combination of JDK and OS (more...)

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly (more...)

When error say nothing about real issue

We want restore backup from source. So we took backup from source and copied it to /dba/share/MYDB on target. My collouge sent me email saying  restore failed with following error

rman target /

Recovery Manager: Release - Production on Wed Sep 18 20:47:38 2013

Copyright (more...)