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Dbvisit replicate – SQL Developer chart
Here is a quick SQL Developer report which display a chart about the Dbvisit replicate lag over the last hours The idea is to have the following chart showing the lag in MINE and APPLY processes. Here...
View ArticleQuick history on database growth
AWR collects segment statistics, and this can be used to quickly understand an abnormal database growth. Here is a script I use to get, from the AWR history, the segments that have grown by more than...
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Multitenant dictionary: what is consolidated and what is not
The documentation says that for Reduction of duplication and Ease of database upgrade the Oracle-supplied objects such as data dictionary table definitions and PL/SQL packages are represented only in...
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Multitenant internals: INT$ and INT$INT$ views
This month, I’ll talk – with lot of demos – about multitenant internals at DOAG conference. The multitenant dictionary architecture starts with a simple idea: system metadata and data are in CDB$ROOT...
View ArticleDynamic Sampling vs. Extended Statistics
On datawarehouse databases, I frequently recommend increasing the level of dynamic sampling because: Queries have complex predicates with AND, OR, IN(), ranges and correlated values for which the...
View ArticleCBO, FIRST_ROWS and VIEW misestimate
There are several bugs with the optimizer in FIRST_ROWS mode. Here is one I encountered during a 10.2.0.4 to 12.2.0.1 migration when a view had an ‘order by’ in its definition. Here is the test case...
View ArticleUnstructured vs. structured
The title of this blog post was: “Tracing DBMS_RCVMAN for reclaimable archivelogs” until I started to write the conclusion… In a previous post I mentioned that there’s a bug with archivelog deletion...
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12c Multitenant Internals: compiling system package from PDB
When I explain the multitenant internals, I show that all metadata about system procedures and packages are stored only in CDB$ROOT and are accessed from the PDBs through metadata links. I take an...
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#DOAG2017
The discussions about the technologies we love. With Bryn about my tests on the MLE and the fact that I compared very different things, running a recursive function on different datatype (integer vs....
View Articleimpdp logtime=all metrics=y and 12cR2 parallel metadata
A quick post to show why you should always use LOGTIME=ALL METRICS=Y when using Data Pump. Just look at an example showing the timestamp in front of each line and a message about each task completed by...
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#UKOUG_TECH17
Award I’ve received an award for an article I’ve written last year, the Most Read Oracle Scene Article in 2016 – Technology. I like to write for Oracle Scene magazine. It is rare today to have a...
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Oracle docker image from docker store
Did you notice that each time you want to download the Oracle binaries from the OTN website (for non-production usage) you have to click on the “Accept License Agreement”? This is because you have to...
View Article12cR2 Subquery Elimination
More and more we can see crazy queries generated by ORM frameworks or BI query generators. They are build to be easily generated rather than being optimal. Then, the optimizer has to implement more and...
View ArticleDrop PDB including datafiles may keep files open
I like that Oracle drops the datafiles from the operating system when we remove them from the database (with drop tablespace or drop pluggable database) because I don’t like to have orphean files...
View Article12c Multitenant internals: PDB replay DDL for common users
In multitenant, you can create common Users, Roles, and Profiles. You create them in CDB$ROOT, with the CONTAINER=ALL clause (which is optional because it is the only possible value when connected to...
View Article12c Multitenant internals: PDB_PLUG_IN_VIOLATIONS
In the previous post https://blog.dbi-services.com/12c-multitenant-internals-pdb-replay-ddl-for-common-users I’ve done some DDL on a common user to show how this is replayed later for PDBs that were...
View ArticleKeep your orapw password file secure
This is a small demo I did when I’ve found a database password file (orapw) lying around in /tmp with -rw-rw-rw- permissions, to show how this is a bad idea. People think that the orapw file only...
View ArticleSpectre and Meltdown, Oracle Database, AWS, SLOB
Last year, I measured the CPU performance for an Oracle Database on several types of AWS instances. Just by curiosity, I’ve run the same test (SLOB cached reads) now that Amazon has applied all Spectre...
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Spectre/Meltdown on Oracle Public Cloud UEK – PIO
The Spectre and Meltdown is now in the latest Oracle UEK kernel, after updating it with ‘yum update': [opc@PTI ~]$ rpm -q --changelog kernel-uek | awk '/CVE-2017-5715|CVE-2017-5753|CVE-2017-5754/{print...
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Spectre and Meltdown on Oracle Public Cloud UEK – LIO
In the last post I published the strange results I had when testing physical I/O with the latest Spectre and Meltdown patches. There is the logical I/O with SLOB cached reads. Logical reads I’ve run...
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