quarta-feira, 28 de setembro de 2022

How to study for 1z0-149 - Oracle Database PL/SQL Developer Certified Professional

Hi all,I had 2 vouchers(Now, it's called "Oracle Exam Attempt") to use until the end of September and I decided to take the PL/SQL 19c exam.My first thought was " I'll give it a try, I don't think much has changed since 11g".And I was completely wrong!I didn't study, just scheduled the exam and got a really bad result!After a week of studying the new features and reviewing many concepts, I got a good score :)If you have ULS, this is a good starting...

segunda-feira, 26 de setembro de 2022

Upgrade From 11.2.0.4: Slow Performance Adding Nullable Columns With Default Values To AWR Tables

Hi all,I was in a project where the customer upgraded a large production database from 11g to 19c.Phase 0 of the upgrade process took almost 4 hours and the DDLs responsible for all that time were related to new columns on AWR tables (WRH$ tables).I was talking to Rodrigo Jorge (PM for upgrades and migrations) and he pointed me to this patch: 30387640For example, these 2 DDLs took about 2 hours to run:alter table WRH$_SQLSTAT add (obsolete_count...

quinta-feira, 22 de setembro de 2022

Downgrading Oracle Database to an Earlier Release

Hi all,I was in a project where the customer had one database in a training environment to upgrade from 11g to 19c.The customer requirement was to have a fallback option in case of any issue in the next few days.The fallback option during the upgrade is to create a GUARANTEE RESTORE POINT. But after a few days, you can lose data in case you go back to the restore point.To be honest, I have never seen a downgrade in all my Oracle life, but it was...

quinta-feira, 15 de setembro de 2022

Row Count + DBMS_COMPARISON - Logical Replication

Hi all, I was in a project where logical replication was in place.It was going from 11g non-exa to 19c on Exadata and they ran into some issues during their last migration attempt a year ago.At that time OGG was sending data from 11g to 19c and another third-party tool was sending from 19c back to 11g (in case of rollback needed). The problem was that this tool is based on triggers to capture and DML commands to replicate, but you can imagine how bad it is when you have a large number of transactions and 2 database nodes.Now, they decided to use...

terça-feira, 13 de setembro de 2022

How to study for 1Z0-997-22 - Oracle Cloud Infrastructure 2022 Architect Professional

Hi all,I decided to take all the 2022 OCI exams to check what changed and guide people in taking these certifications.Well, not all exams. I will do only the ones that I did in 2019/2020/2021 and are the things that I work on a day-to-day basis 🙂On this test, I was expecting to see some new things(comparing the course topics with the previous years). And that's true, I got a lot of new questions.Of course, I don't remember the question from...

segunda-feira, 12 de setembro de 2022

Database Migration/Upgrade - Performance Advice

Hi allI was on a project where logical replication (OGG) was used to move a critical database from 11g non-exa to 19c on Exadata with the smallest downtime possible.In terms of performance, for the top 100 SQLs, we had 96 improvements including SQLs running 40x faster due to smart scans. But, we had 6 regressions.One SQL went from 0.2 ms to 0.6 ms.I know you are thinking: “not a big deal”.But when this SQL is executed in a batch process millions of times, the batch time goes from 42 minutes to 126 minutes and it can cause a lot of problems for...

quinta-feira, 8 de setembro de 2022

How to study for 1z0-931-22 - Oracle Autonomous Database Cloud 2022 Professional

Hi all,I decided to take all the 2022 OCI exams to check what changed and guide people in taking these certifications.Well, not all exams. I will do only the ones that I did in 2019/2020/2021 and are the things that I work on a day-to-day basis 🙂On this test, I was expecting to see a few new things(comparing the course topics with the previous years). I don't remember the question from the 2021 exam (did it one year ago), but I was not...

segunda-feira, 5 de setembro de 2022

How to study for 1z0-1093-22 - Oracle Cloud Database Services 2022 Professional

Hi all,I decided to take all the 2022 OCI exams to check what changed and guide people in taking these certifications.Well, not all exams. I will do only the ones that I did in 2019/2020/2021 and are the things that I work on a day-to-day basis 🙂On this test, I was expecting to see a few new things(comparing the course topics with the previous years). I don't remember the question from the 2021 exam (did it one year ago), but I was not...