Uwe Hesse

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Oracle University Expert Summit 2015 in Dubai

Oracle University Expert Summit Dubai 2015

Together with Craig Shallahamer, Lucas Jellema, Mark Rittman, Martin Bach, Pete Finnigan and Tim Fox, I will be presenting in Dubai. My topic is Minimizing Downtime with Rolling Upgrade using Data Guard

Click on the picture for details, please!

Hope to see you there :-)

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#DOAG2014 bits of info for DBAs

Just wanted to share some pieces of information from the recent DOAG annual conference that you may find interesting.

From Mike Dietrich’s presentation about Database Upgrade:

Mike Dietrich

Database Replay is extremely useful to predict after-upgrade performance on a test system,

especially we can record the production load on 10g even.

From Carsten Czarski’s talk about XML DB:

Carsten Czarski

With 12c, XML DB is mandatory and it provides an easy way to upload BLOBs via ftp into the database.

From Ulrike Schwinn’s talk about the Resource Manager I took away that

The resource manager becomes more and more popular and important, especially for Multitenant

– something Hans Forbrich reinforced later on.

Particularly I liked way she presented later on about ADO: Very many live demonstrations – that’s how I try to do my own presentations also :-)

Ulrike Schwinn

Frank Schneede did a great job debunking Exadata myths. For example,

You don’t need to have all cores enabled with Exadata X4 in order to save license cost. That’s called Capacity on Demand.

Frank Schneede

If I should name one presentation that was most useful for me, it’ll be probably Frank’s.

Markus Michalewicz delivered an excellent talk as expected about RAC cache fusion:

Markus Michalewicz

Two important messages:

RAC scales well (far) beyond three nodes because there are never more than three nodes involved for cache fusion intercommunication.

And Multitenant and RAC are a perfect fit.

One Data Guard snippet out of Larry Carpenter’s talk about Global Data Services (GDS):

GDS makes it possible to automate the failover of the Real-Time Query service to the primary in case the physical standby has an outage.

Larry Carpenter

Hans Forbrich talked about Multitenant. He showed great presentation skills and although I knew the technical details before, the way he highlighted certain aspects was still very helpful for me.

Hans Forbrich

One key message was that

Multitenant is here to stay.

DBAs should learn about it and become familiar with it as soon as possible,

because sooner than later it will have to be administered in production!

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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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