Why EXCLUDE_SEED_CDB_VIEW is now an underscore in Oracle 12.2

Hiding information is not good - and exclude_seed_cdb_view is now an underscore in Oracle 12.2I have received several questions from customers in the past weeks using Oracle Multitenant about the parameter exclude_seed_cdb_view.It magically disappeared and morphed into _exclude_seed_cdb_view since Oracle Database To be fair, the exclude_seed_cdb_view is listed in the list of obsolete parameters in Oracle Database


This parameter hides everything belonging to the PDB$SEED from the usual queries.… [Read More]

SGA_MIN_SIZE in Oracle Database 12.2

I did summarize all new init.ora/spfile parameters in Oracle Database a while ago:

New SPFILE parameters in Oracle Database

And one caught Roy’s and my attention: SGA_MIN_SIZE.

When we present this new parameter as part of the Multitenant slides in our workshops, some people ask themselves:
“What happens if I oversubscribe such a parameter?” For example, if SGA_TARGET=4G and I have 10 PDBs and define in each of them SGA_MIN_SIZE=500M.… [Read More]

PGA_AGGREGATE_LIMIT enforces default since Oracle Database

The init.ora/spfile parameter PGA_AGGREGATE_LIMIT got introduced in Oracle Database

As per documentation in Oracle Database 12.1 it got defined as:

PGA_AGGREGATE_LIMIT specifies a limit on the aggregate PGA memory consumed by the instance.“.

Furthermore the algorithm for its setting got described as:

By default, PGA_AGGREGATE_LIMIT is set to the greater of 2 GB, 200% of PGA_AGGREGATE_TARGET, and 3 MB times the PROCESSES parameter.[Read More]

New SPFILE parameters in Oracle Database with July 2016 (and newer) PSU/BP

New Parameters in Oracle Database with July 2016 PSU/BP

By following an internal discussion and checking parameter changes between Patch Set Updates (PSU) and Proactive Bundle Patches (BP) I learned that we introduced two new SPFILE parameters in Oracle Database with the July PSU and BP. One is documented in the patch readme, the other one can be found right now only in the Oracle Database manual:

The Oracle 12.2 documentation about ALLOW_GROUP_ACCESS_TO_SGA, the parameter which appears not in the Oracle 12.1 documentation right now, says:

ALLOW_GROUP_ACCESS_TO_SGA controls group access to shared memory on UNIX platforms.

[Read More]

Default Changes SPFILE Parameters – Oracle 12.2

This is the 4th posting in my series about init.ora/SPFILE parameters in Oracle Database

Roy and I did a comparison between default parameter settings in Oracle Database vs Oracle Database vs Oracle Database… [Read More]

Enabling Oracle 12.2 ADAPTIVE Features in Oracle

Oracle Database 12.2 introduces the new split-up adaptive parameters, OPTIMIZER_ADAPTIVE_PLANS and OPTIMITER_ADAPTIVE_STATISTICS. And the key trigger to cure potential and known performance issues in Oracle Database is enabling Oracle 12.2 ADAPTIVE Features in Oracle

For more information please see:

Enabling Oracle 12.2 ADAPTIVE Features in Oracle

But Oracle Database 12.2 on-premises is not out yet – so what should you do when upgrading to Oracle Database 12.1 – or struggling with some of the “adaptive” features in Oracle 12.1?… [Read More]


The Oracle Database 12.1 parameter OPTIMIZER_ADAPTIVE_FEATURES has been made OBSOLETE (i.e. must be removed from the SPFILE when upgrading) in Oracle Database 12.2.

It gets replaced with two parameters of whom one is enabled, the other one is disabled by default:


Nigel Bayliss, our “Optimizer” Product Manager has blogged about it already with way more detailed insights.… [Read More]