This week I attended the RMOUG (Rocky Mountain Oracle User Group) conference in Denver, Colorado. It was my first time attending RMOUG and I must say that although it's not a very big event (I think around 350 attendees), I was very impressed by the quality of the event and the great content which was presented by very good speakers. I highly recommend it to anybody who considers attending next year's RMOUG. It's a great place to network, learn, and have fun.
I presented 2 sessions. The slide decks are now available:
Last week, ILOUG (Israel Oracle User Group) hosted an awesome Oracle conference in Israel which included 30 Oracle speakers from 9 countries and 45 different sessions. This event was organized by Ami Aharonovich, Zohar Elkayam, and Oren Nakdimon, all good friends and Oracle ACEs. It was a very well organized event, and awesome content which was delivered by 19(!) Oracle ACEs. In addition, there was a presence of Oracle Product Management as both Maria Colgan and Gerald Venzl attended and delivered several great sessions including an Oscar-candidate show of the IT Wars (DBA vs. Developer). Also worth mentioning, Chris Saxon from Oracle presented an awesome SQL magic show :)
I'd like to share with you my plans for my upcoming speaking activities for the first half of 2018.
Israel Oracle User (ILOUG) Group Tech Days 2018 (Jan 22-23) - very excited to present a session in one of the best Oracle conferences that ever took place in my country. I will be presenting a session titled "Winning Performance Challenging in Oracle Multitenant" on January 23rd about how to effectively monitor and diagnose performance issues in Oracle Multitenant environments and if needed implement resource management plans to ensure high QoS (Quality of Service) for the pluggable databases.
Rocky Mountain Oracle User Group (RMOUG) Training Days (Feb 20-22) - This will be my first time attending (and speaking) at this event. I will deliver 2 sessions:
"Winning Performance Challenging in Oracle Multitenant"- similar to the one I will be presenting at ILOUG
"Oracle Database Locking Mechanism Demystified" - In this session I will be talking about the concepts of Oracle Database locking mechanism, advanced locking scenarios, best practices to avoid performance issues which relate to blocked SQLs, and ways to investigate lock issues using Oracle dictionary views and performance monitoring tools
Independent Oracle User Group (April 22-26) - IOUG Collaborate is definitely my favorite Oracle Conference in the world - it's a combination of great location and very good and technical presentations. I got accepted to present the following sessions:
ASM Concepts, Architecture and Best Practices - Since it was introduced back in 2003 with Oracle 10g, ASM became an essential part of almost every Oracle DBA's life. In this session you will learn ASM from A to Z - starting with the basic concepts of the ASM all the way to the new features of ASM and important best practices that will help you increase the performance and stability of your Database environments.
Oracle Data Guard for Beginners - Oracle Data Guard is one of the most important options in the Oracle Database as it allows organizations to ensure high availability, data protection, and disaster recovery for their Oracle database environments. In this session we'll review Oracle Data Guard solution from A to Z.
I invite you all to my sessions and looking forward to meeting you there!
Yesterday I received the following email from the Oracle ACE Program:
"I am pleased to inform you that you have been accepted to receive the Oracle ACE award. You have been chosen based on your significant contribution and activity in the Oracle technical community. Like your fellow Oracle ACEs, you have demonstrated a proficiency in Oracle technology as well as a willingness to share your knowledge and experiences with the community."
I received this recognition from Oracle and I'm proud the be part of the awesome Oracle ACE family - thank you Oracle ACE Program!
Thank you IOUG (Independent Oracle User Group) for choosing me to present sessions at IOUG Collaborate 16 & 17 and also for inviting me to present on behalf of the IOUG at Oracle OpenWorld 2016 & 2017. I would also like to thank additional local user groups: DOAG, AOUG, OUNG for choosing me to speak at their annual user group conferences.
I've decided to dedicate my ODC Appreciation Day blog post to "Online Move Data File Operation" - a feature which has been introduced in Oracle 12c. As a quick background to this blog post, ODC (Oracle Developer Community) appreciation day is Tim Hall's (Oracle-Base) initiative which started last year (when it was OTN Appreciation Day).
So what is online move data file operation?Moving data files is a common-use case, for example, when the DBA would like to move data files to a faster/larger disk. Another common use case is when DBA would like to migrate the files from traditional file systems to Oracle's Automatic Storage Management (more information about Oracle ASM is available in my ODC published article : https://community.oracle.com/docs/DOC-995178)
Prior to Oracle 12c, there was no way to accomplish this task with zero downtime. Common solution was to take the entire tablespace or data file offline, move it to the new location, change the location using the "ALTER DATABASE" command (which essentially changes the location in the Oracle's control file) and then bring the tablespace/file online again; however, during this operation the entire tablespace or datafile won't be accessible. Better approach to mitigate the downtime was to change the tablespace or data file to be in a read-only mode which will at least allow queries to be executed against the data which reside on that tablespace/file - but it's still not favorable because DMLs/DDLs cannot be executed during that operation.
Oracle 12c allows us to do this completely online with zero downtime - while the database is open and users are accessing the data file. I've presented this feature with several syntax examples as part of my IOUG Collaborate 16 presentation - "Best New Features of Oracle Database 12c" (slide deck is available here: https://www.slideshare.net/PiniDibask/best-new-features-of-oracle-database-12c).
SummaryWhether running Oracle databases on premise or in the cloud, this feature is very useful. When Larry Ellison spoke at Oracle OpenWorld 2017 keynotes about Oracle 18c and Oracle's option of to ensure having up to 30 minutes down-time a year with their cloud offering, this feature is another useful way that can help when it comes to ensuring zero impact on the customer's applications (among the many other Oracle's HA & DR features - such as ASM, RAC Rolling Upgrades, Active Data Guard, Flashback, etc.)
Last week, on October 1st, I've presented a session at Oracle OpenWorld about Database consolidation using Oracle Multitenant option. I was invited to speak on behalf of the IOUG (Independent Oracle User Group) at Oracle OpenWorld for the second year in a row! Thank you IOUG for this great opportunity! It was fun (as always).
IntroductionIn today's blog post, I'd like to uncover a common misconception about how Oracle handles deadlocks, but first let's talk about what deadlock is. Deadlock is a locking scenario that occurs when two or more sessions are blocked as they wait because of a lock that is being held by the other session. Oracle Database automatically detects this scenario and handles this because otherwise, they will wait forever as both of them are blocked and waiting to each other’s locked resources. But the question is how does Oracle handle this? some would say that Oracle handles these scenarios by terminating one of the sessions which is known to be as the "deadlock victim" - well, that's wrong. Others would say that by rolling-back the entire transaction of one of the sessions - well, that's also wrong. So how Oracle really handles deadlock scenarios?
Let's see a quick example of how deadlock occurs
Step 1 Session #1 performs an update of a row (employee #151) and acquires a lock on that row
SQL> UPDATE employee SET first_name = 'David' WHERE employee_id = 151;
1 row updated.
Session #2 performs an update of a row (employee #39) and acquires a lock on that row
SQL> UPDATE employee SET first_name = 'Greg' WHERE employee_id = 39;
1 row updated.
Step 3 Session #1 performs an update of a row (employee #39) and is now waiting since a lock has been acquired on the same row which has not been released yet as session #2 transaction is still active
UPDATE employee SET first_name = 'Mark' WHERE employee_id = 39;
Session #2 performs an update of a row (employee #151) and is now waiting since a lock has been acquired on the same row which has not been released yet as session #1 transaction is still active.
SQL> UPDATE employee SET first_name = 'John' WHERE employee_id = 151;
At this stage both sessions (session #1 and session #2) are blocked and waiting to each other’s locked resources - that's exactly what deadlock is. So how Oracle handles deadlock scenarios?
The way Oracle handles deadlock scenarios is not by terminating one of the sessions or performing a transaction-level rollback, it's actually just by performing a statement-level rollback to one of the sessions. The session that its statement is being rolled back, will encounter an “ORA-00060: Deadlock detected while waiting for resource.” error message (that will also be recorded in the alert log file).
Last week (on June 20th) I presented a session about the Oracle Database Locking Mechanism at the Austrian Oracle User Group (AOUG) conference. This event took place in beautiful Vienna and was my first attending this event. It's a small, one-day event . There were 180 attendees - small, but still very fun well-organized. I particularly enjoyed the keynote of Maria Colgan & Gerald Venzl (both Product Managers for Oracle) about Oracle Database 12c and DevOps - it was a very amusing show in which Maria played the role of the DBA and Gerald played the role of the developer and together they showed how they can work together happily by leveraging Oracle Database 12c features and technologies. Another session that I particularly enjoyed was presented by Maris Elsins about Mining the AWR and how to find alternative Methods for Identification of the Top SQLs in order to address various performance issues.
You can find in event page links to my presentation as well as other presentations from this event. I'd like to thank everyone who attended my session, and I hope to see you again next year.
In many companies there is a clear separation of duties for various Oracle Database related tasks such as administering ASM and backing up/restoring Oracle databases.
In the past, DBAs used SYSDBA permission for administering ASM and RMAN. As you probably know, SYSDBA is the most powerful permission in Oracle Database which even allows viewing all the application data.
Oracle realized that they need to address the separation of duties requirement of many customers and therefore they have provided in Oracle 11g a dedicated permission for administering ASM - I've written a dedicated blog post in the past for this matter. The SYSASM permission cannot access application data, but it can perform various ASM related management tasks (such as altering diskgroup, adding disks, etc.)
What about RMAN?
Until Oracle Database version 12cR1, there wasn't a good solution from a separation of duties when it comes to RMAN backups as users had to use SYSDBA which also allows them to access any application data (as well as other strong permissions).
In Oracle 12cR1, Oracle introduced the SYSBACKUP permission which allows a user to perform backup and recovery operations either from Oracle Recovery Manager (RMAN) or SQL*Plus.
You can view here the full list of operations allowed by this administrative privilege
And what about Data Guard?
Very similar to RMAN, Oracle also introduced in version 12cR1 a dedicated privilege named SYSDG which can be used with the Data Guard Broker and the DGMGRL command-line interface.
First, we can connect to a 12c instance and look for those accounts. Next step would be to connect / AS SYSBACKUP since I'm logged with a user that has OS permissions to connect without any username and password
SQL> SELECT username, account_status FROM dba_users WHERE username LIKE '%SYS%';
Note that in order to connect to the database as either SYSDG or SYSBACKUP using a password, there must be a password file for it because it is possible to connect even when the database is not up and running, as follows
Total System Global Area 1644167168 bytes Fixed Size 8793400 bytes Variable Size 989856456 bytes Database Buffers 637534208 bytes Redo Buffers 7983104 bytes Database mounted. SQL> connect c##pini/pini ERROR: ORA-01033: ORACLE initialization or shutdown in progress Process ID: 0 Session ID: 0 Serial number: 0 Warning: You are no longer connected to ORACLE.
SQL> connect c##pini/pini as SYSBACKUP; Connected.
SummaryIn this post we've reviewed the SYSDG and SYSBACKUP users and permissions in Oracle 12c which could be useful in case that in your company there is a requirement to have a separation of duties for backup/recovery as well as for Data Guard related administration tasks. I hope you find it useful for you.
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