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January 2014

Implementing Deferred Segment Creation After an Upgrade

I have written previously about Deferred Segment Creation. Each empty table and its indexes use only 64Kb (assuming an 8Kb block size and locally managed tablespaces), but in a PeopleSoft there can be be tens of thousands of such tables and that adds up to a saving worth making.

If you are upgrading your database to 11gR2 , you might want to make sure that you are using it.  Deferred segment creation was introduced in Oracle 11.2.0.2 and it became the default in 11.2.0.3.  However, any table created in a previous version will have a physical segment.

This problem could affect any system, but it also manifests itself in PeopleSoft in a particular way.

Implementing Deferred Segment Creation After an Upgrade

I have written previously about Deferred Segment Creation. Each empty table and its indexes use only 64Kb (assuming an 8Kb block size and locally managed tablespaces), but in a PeopleSoft there can be be tens of thousands of such tables and that adds up to a saving worth making.

If you are upgrading your database to 11gR2 , you might want to make sure that you are using it.  Deferred segment creation was introduced in Oracle 11.2.0.2 and it became the default in 11.2.0.3.  However, any table created in a previous version will have a physical segment.

This problem could affect any system, but it also manifests itself in PeopleSoft in a particular way.

Data Guard transport lag in OEM 12c

I have come across this phenomenon a couple of times now so I thought it was worth writing up.

Consider a scenario where you get an alert because your standby database has an apply lag. The alert is generated by OEM and when you log in and check-it has indeed an apply lag. Even worse, the apply lag increases with every refresh of the page! I tagged this as an 11.2 problem but it’s definitely not related to that version.

Here is a screenshot of this misery:

 Lag in OEM

Now there are of course a number of possible causes:

New member of The OakTable: me!

I am an Oakie now :-)

OakTableLogo

 

 

To be a part of this highly respected circle of Oracle Scientists is something that I consider one of the greatest achievements of my professional life.

Recurring Conversations – Incremental Statistics (Part 1)

When I first started blogging, most of the material came from issues that I'd run into and how they were solved but, as I've spent most of the last 7 months not logging in to anything much ;-), it occurred to me that another area which I haven't used for a long time is what I'll call recurring conversations.

The Oracle Instructor

DocDB a short description

Docdb is a tool, to automatically document your plsql database.

DocDB a short description

Docdb is a tool, to automatically document your plsql database.

Justification of Laws Limiting Individual Freedom

Justification of Laws Limiting Individual Freedom

Humans have a right to seek joy by any means that does not prevent or reduce the joy of others. Any other stance is an expression of religious views, which I respect, but which should not be promulgated by the government.

Therefore, any law must be to either:

a)      Create facilities for the joy of all
b)     Restrict freedom for the purpose of preventing one person from depriving another of joy or the possibility of joy.

In the cases where law is promulgated in support of the creation of facilities for the joy of all, the laws should be as efficient as possible.

In the cases where law is promulgated in support of prevention of the preemption of the joy of others, the minimum restriction must be sought, and any notion that limiting any person’s joy because others might be jealous or envious of greater joy must be rejected.

Examples:

Category A:

'active txn count during cleanout', part I

I was going to write a blog post about some peculiar side effects you can get into with the delayed block cleanout when running parallel DML but soon discovered that the entry became so big that I've decided to split it up into a series of more manageable posts.

For a good background on various themes of block cleanout check out Clean it up by Jonathan Lewis.

Active transactions, consistent reads and table scans

First I'm going to show you some interesting observations about what happens when you're trying to select from the block which has an outstanding open transaction in it. Let's create a test table with one row and update it leaving the transaction open. I'm using 11.2.0.4 here:





SQL> create table test (n number, m number);

Table created

SQL> insert into test values (1, 1);

1 row inserted

SQL> commit;