Foreign Archived Log in #Oracle – what does it mean?

When you look into V$RECOVERY_AREA_USAGE, you see a strange row at the bottom:

SQL> select * from v$recovery_area_usage;

FILE_TYPE               PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES     CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
CONTROL FILE                             0                         0               0          0
REDO LOG                                 0                         0               0          0
ARCHIVED LOG                         10.18                         0              73          0
BACKUP PIECE                             0                         0               0          0
IMAGE COPY                               0                         0               0          0
FLASHBACK LOG                            0                         0               0          0
FOREIGN ARCHIVED LOG                     0                         0               0          0
AUXILIARY DATAFILE COPY                  0                         0               0          0

Curious what that could be? You will see values other than zero on a Logical Standby Database:

SQL> connect sys/oracle@logst as sysdba
Connected.
SQL> select database_role from v$database;

DATABASE_ROLE
----------------
LOGICAL STANDBY

SQL> select * from v$recovery_area_usage;

FILE_TYPE               PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES     CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
CONTROL FILE                             0                         0               0          0
REDO LOG                                 0                         0               0          0
ARCHIVED LOG                         14.93                         0               9          0
BACKUP PIECE                             0                         0               0          0
IMAGE COPY                               0                         0               0          0
FLASHBACK LOG                            0                         0               0          0
FOREIGN ARCHIVED LOG                  2.03                         0              26          0
AUXILIARY DATAFILE COPY                  0                         0               0          0

In contrast to a Physical Standby Database, this one writes not only into standby logs but also into online logs while being in standby role. That leads to two different kinds of archive logs:
Foreign Archived LogsWhen DML (like insert and update) is done on the primary 1) that leads to redo entries into online logs 2) that are simultaneously shipped to the standby and written there into standby logs 2) also. The online logs on the primary and the standby logs on the standby will be archived 3) eventually. So far that is the same for both physical and logical standby. But now a difference: Logical standby databases do SQL Apply 4) by logmining the standby or the archive logs that came from the primary. That generates similar DML on the standby which in turn leads LGWR there to write redo into online logs 5) that will eventually get archived 6) as well.

A logical standby could do recovery only with its own archive logs (if there was a backup taken before) but not with the foreign archive logs. Therefore, those foreign archive logs can and do get deleted automatically. V$ARCHIVED_LOG and V$FOREIGN_ARCHIVED_LOG can be queried to monitor the two different kinds of logs.

That was one topic of the course Oracle Database 12c: Data Guard Administration that I delivered as an LVC – therefore the picture. Hope you find it useful :-)

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Presentations to go to at #DOAG2014

As every year, there’s a long list of great speakers with interesting talks to attend at the DOAG (German Oracle User Group) annual conference. Sadly I cannot attend them all, so I’ve got to make a choice:

First day

Datenbank-Upgrade nach Oracle 12.1.0.2 – Aufwand, Vorgehen, Kunden by Mike Dietrich, Oracle

Die unheimliche Begegnung der dritten Art: XML DB für den DBA by Carsten Czarski, Oracle

Advanced RAC Programming Features by Martin Bach, Enkitec

Automatische Daten Optimierung, Heatmap und Compression 12c live by Ulrike Schwinn, Oracle

Second day

Understanding Oracle RAC Internals – The Cache Fusion Edition by Markus Michalewicz, Oracle

Die Recovery Area: Warum ihre Verwendung empfohlen ist – I have to go to that one because I present it myself :-)

Geodistributed Oracle GoldenGate and Oracle Active Data Guard: Global Data Services by Larry Carpenter, Oracle

Oracle Database In-Memory – a game changer for data warehousing? by Hermann Baer & Maria Colgan, Oracle

Oracle Distributed Transactions by Joel Goodman, Oracle

Third day

High Noon – Bessere Überlebenschancen beim Datenbank Security Shoot Out by Heinz-Wilhelm Fabry, Oracle

Tuning Tools für echte Männer und Sparfüchse – vom Leben ohne EM12c by Björn Rost, portrix Systems

Best Practices in Managing Oracle RAC Performance in Real Time by Mark Scardina, Oracle

Maximum Availability with Oracle Multitenant: Seeing Is Believing by Larry Carpenter, Oracle

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Digital Learning: LVC customer quotes

LVC

Here’s a collection of customer quotes as a follow-up to my last post about the importance of attitude towards Live Virtual Classes (LVCs). They are from courses that I have taught personally this year with an average delivery score of about 96%:

Oracle Database 12c: Managing Multitenant Architecture

Oracle Grid Infrastructure 11g: Manage Clusterware and ASM

Oracle Database 12c: New Features for Administrators

Exadata Database Machine Administration Workshop

Oracle 11g: RAC and Grid Infrastructure Administration Accelerated

“My first experience of an LVC. Pleased to say it was very positive. Introduction and start on Monday morning was smooth. I would recommend to my colleagues.”

Always important to make a good first impression!

“The whole LVC package just worked. From the comfort of my own environment with a great instructor makes for happy learning :)”

And that is exactly what we strive to deliver.

“Both, host and producer were very professional and guided the students through the course.”

An LVC producer takes care for all technical aspects apart from the course itself, like access to the learning platform. The instructor appears as “host” on the learning platform.

“Instructor professionally answered students’ questions and kept up a positive mood in the community!”

LVCs can be funny too :-)

“I appreciate the way how the course was presented. Very well controlled time, organization of presentation, exercises. Interaction with us was great. Always ready to answer a question, give an examples to difficult topic, illustrating topics.”

So much about allegedly missing interaction in LVCs.

“I work few years on RAC databases, my knowledge was not so clear regarding some topic on RAC and Grid after completing this training I’m sure that I will handle our RAC and Grid environment differently and for sure will have positive impact in our production environment. Great thank!”

You cannot top that with a classroom course either :-)

“LVC is offering great and flexible way to gain knowledge without travel or hotels etc.”

“LVCs reduce travel costs and help the students to manage their time on their own, i.e. to join the classes from home and focus on the presented content.”

Trust me, I didn’t make up the last two although they may sound like your manager talking – or mine, for that matter ;-)

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