Oracle Cloud: How to create a database link?

25. November 2020 Uncategorized 1
On my journey to the Oracle Cloud, I got another task to complete – to create a database link between two databases running on the Oracle Cloud. I will cover the use case of creating a database link between databases in a separate regions (Switzerland > Frankfurt). Database link between databases in a separate region ...

Oracle Cloud: Some issues with the old IMP & EXP utilities

14. November 2020 Uncategorized 0
As I am still helping one customer to explore the Oracle Cloud, I am learning myself something new every time and I am also facing some issues on that way. The last one is related to the old IMP and EXP tools. One of the automated steps is to export some tables from one database ...

Oracle Cloud: ORA-00018 maximum number of sessions exceeded -> Use DRCP

08. November 2020 Uncategorized 2
One of my customers want to try out the Oracle Cloud, and they started with a small database using the “Always Free” option. So far, so good, except one issue – from time to time, they are getting the error message “ORA-00018: maximum number of sessions exceeded“. Every Oracle DBA would first check the database ...

Using one Client with multiple Oracle wallets

16. October 2020 Uncategorized 1
Last week I got a task from one customer, to set up the Oracle Client, which could seamless connect to multiple databases in the Oracle Cloud, for which we need the Oracle wallet. Let’s say there is one database in the EU region Frankfurt, and the second one is in the EU region Zurich. I ...

Database Upgrade using autoupgrade tool

This time I had to upgrade a SE2 12.2 database running on Windows on Azure Cloud to the version 19.3. I do not have such setup in my lab, so I was a little bit sceptical about it, and it will turn out – with a reason. So, I read a ton of a articles ...

You should take care about statistics!

Ever since Oracle introduced the CBO (Cost Based Optimizer) there were some performance issues, mostly because of missing or staled statistics in the database. I stopped to count the cases, when I just gathered fresh statistics for some table(s) and voilà – the query runs 100x faster! I will mention just one of the latest ...

Wrong result returns when Subquery is unnested

A couple of days ago I got a request to take a look at one SQL query, which obviously returns the wrong result. The database version is 12.2 running on Windows on Azure Cloud. Simplified for the demo purpose it looks like this – the query returns 1 and 2, but it should return 1, ...

LMS0: terminating the instance due to error 481

15. December 2016 Uncategorized 1
One production RAC database has been upgraded to 12c and everything went fine for a couple of months, but suddenly after some time, one instance got terminated with the error messages: LMS2 (ospid: 17238): terminating the instance due to error 481 ORA-00481: LMON process terminated with error   The analysis was not so easy. We ...

DataPatch: patch 23177536: The database must be in upgrade mode <- are you serious!?

29. September 2016 Uncategorized 2
Today I applied the latest patchset 12.1.0.2.160719  (July 2016) and afterwards I executed datapatch tool, but got a really stupid error: [oracle/ACME1@acme01 OPatch]$ sqlplus / as sysdba SQL> select  PATCH_ID, PATCH_UID, VERSION, STATUS, DESCRIPTION      from DBA_REGISTRY_SQLPATCH      order by BUNDLE_SERIES;       no rows selected [oracle/ACME1@acme01 OPatch]$ ./datapatch -verbose SQL Patching tool version 12.1.0.2.0 ...