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Archive for March, 2018|Monthly archive page

DBA Internals of the Oracle Autonomous Database

In Cloud, DBA, Oracle database, Oracle internals on March 28, 2018 at 07:11

First things first: the word autonomous come from the Greek word autónomos which means “with laws of one’s own, independent”.

After starting using the Autonomous Data Warehouse Cloud, I must say I am pleasantly surprised to see something totally new, simple, uncomplicated and effortless, with no additional tuning or re-architecturing of the Oracle databases needed – the underlying Oracle Cloud Infrastructure is super fast and highly reliable.

1. You may connect to ADWC by either using the web interface as you can see above or as a client (I use SQL Developer 17.4) but for the client connection type choose Cloud PDB and not TNS. Your configuration file is a zip file and not a plain text file to what DBAs are used to.

2. You cannot create indexes on columns, you cannot partition tables, you cannot create materialized views, etc. Not even database links. You will get an error message: “ORA-00439: feature not enabled: Partitioning” or “ORA-01031: insufficient privileges”.

ADWC lets you create primary keys, unique keys and a foreign key constraints in RELY DISABLE NOVALIDATE mode which means that they are not enforced. These constraints can be created also in enforced mode, so technically you can create constraints as in a non-autonomous Oracle database.

Note that in execution plans primary keys and unique keys will only be used for single table lookups by the optimizer, they will not be used for joins.

But … you can run alter system kill session!

3. The Oracle Autonomous Data Warehouse interface contains all necessary capabilities for a non-professional database user to create its own data marts and run analytical reports on the data. You can even run AWR reports.

4. You do not have full DBA control as Oracle (in my opinion) uses lockdown profiles in order to make the database autonomous. As ADMIN user, you have 25 roles including the new DWROLE which you would normally grant to all ADWC users created by you. Among those 25 roles, you have GATHER_SYSTEM_STATISTICS, SELECT_CATALOG_ROLE, CONSOLE_ADMIN, etc. You have access to most DBA_ and GV_$ views. Not to mention the 211 system privileges.

5. ADWC configures the database initialization parameters based on the compute and storage capacity you provision. ADWC runs on dozens of non-default init.ora parameters. For example:

parallel_degree_policy = AUTO
optimizer_ignore_parallel_hints = TRUE
result_cache_mode = FORCE
inmemory_size = 1G

You are allowed to change almost no init.ora parameters except few NLS_ and PLSQL_ parameters.

And the DB block size is 8K!

6. I can see 31 underscore parameters which are not having default values, here are few:

_max_io_size = 33554432 (default is 1048576)
_sqlmon_max_plan = 4000 (default is 0)
_enable_parallel_dml = TRUE (default is FALSE)
_optimizer_answering_query_using_stats = TRUE (default is FALSE)

One of the few alter session commands you can run is “alter session disable parallel dml;”

7. Monitoring SQL is easy:

But there is no Oracle Tuning Pack: you did not expect to have that in an autonomous database, did you? There is no RAT, Data Masking and Subsetting Pack, Cloud Management Pack, Text, Java in DB, Oracle XML DB, APEX, Multimedia, etc.

8. Note that this is (for now) a data warehousing platform. However, DML is surprisingly fast too. I managed to insert more than half a billion records in just about 3 minutes:

Do not try to create nested tables, media or spatial types, or use LONG datatype: not supported. Compression is enabled by default. ADWC uses HCC for all tables by default, changing the compression method is not allowed.

9. The new Machine Learning interface is easy and simple:


You can create Notebooks where you have place for data discovery and analytics. Commands are run in a SQL Query Scratchpad.

10. Users of Oracle Autonomous database are allowed to analyze the tables and thus influence on the Cost Based Optimizer and hence on performance – I think end users should not be able to influence on the laws (“νόμος, nomos”) of the database.

Conclusion: The Autonomous Database is one of the best things Oracle have ever made. And they have quite a portfolio of products….

Finally, here is a live demo of the Oracle Autonomous Data Warehouse Cloud:

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