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Oracle database reliable message waits

This blog is about the oracle database wait event ‘reliable message’. It should be noted that normally, this should not be a prominent wait, and if it does so, the most logical cause would be something that is not working as it should, either by oversubscribing something or simply because of a bug.

The reliable message note on My Oracle Support provides a good description:
https://support.oracle.com/epmos/faces/DocContentDisplay?_afrLoop=34595019638128&id=69088.1&_afrWindowMode=0&_adf.ctrl-state=15ief27plw_97

What’s new with Oracle database 11.2.0.4.200714 versus 11.2.0.4.201020

This blogpost takes a look at the technical differences between Oracle database 11.2.0.4 PSU 200714 (july 2020) and PSU 201020 (october 2020). This gives technical specialists an idea of the differences, and gives them the ability to assess if the PSU impacts anything.

Functions

What’s new with Oracle database 12.1.0.2.200714 versus 12.1.0.2.201020

This blogpost takes a look at the technical differences between Oracle database 12.1.0.2 PSU 200714 (july 2020) and PSU 201020 (october 2020). This gives technical specialists an idea of the differences, and gives them the ability to assess if the PSU impacts anything.

Functions

About the oracle database and compiling and linking.

This blogpost is about how the oracle database executable created or changed during installation and patching. I take linux for the examples, because that is the version that I am almost uniquely working with. I think the linux operating is where the vast majority of linux installations are installed on, and therefore an explanation with linux is helpful to most of the people.

The first thing to understand is the oracle executable is a dynamically linked executable. This is easy to see when you execute the ‘ldd’ utility against the oracle executable:

What’s new with Oracle database 12.2.0.1.200714 versus 12.2.0.1.201020

This blogpost takes a look at the technical differences between Oracle database 12.2.0.1 PSU 200714 (july 2020) and PSU 201020 (october 2020). This gives technical specialists an idea of the differences, and gives them the ability to assess if the PSU impacts anything.

Functions

What’s new with Oracle database 18.11 versus 18.12

This blogpost takes a look at the technical differences between Oracle database 18 RU 11 (july 2020) and RU 12 (october 2020). This gives technical specialists an idea of the differences, and gives them the ability to assess if the RU impacts anything.

Functions

What’s new with Oracle database 19.9 versus 19.8

This blogpost takes a look at the technical differences between Oracle database 19 RU 8 (july 2020) and RU 9 (october 2020). This gives technical specialists an idea of the differences, and gives them the ability to assess if the RU impacts anything.

Functions

Oracle library cache cursor child generation

This post is about library cache SQL cursors, and how these are managed by the database instance.

Oracle multi-tenant and library cache isolation

This post is the result of a question that I got after presenting a session about Oracle database mutexes organised by ITOUG, as a response to the conference cancellations because of COVID-19. Thank Gianni Ceresa for asking me!

The library cache provides shared cursors and execution plans. Because they are shared, sessions can take advantage of the work of previous sessions of creating these. However, by having these shared, access needs to be regulated not to have sessions overwrite each other’s work. This is done by mutexes.

The question I got was (this is a paraphrased from my memory): ‘when using pluggable databases, could a session in one pluggable database influence performance of a session in another pluggable database’?

Oracle rowcache fastgets

This blogpost is about the Oracle database row or dictionary cache. This is a separate cache that caches database metadata, like database object properties or user properties.

There is surprising little in-depth technical detail about the row cache. To some degree I understand: issues with the row cache are rare.

I noticed a column in V$ROWCACHE called ‘FASTGETS’. Whatever FASTGETS means, in my database it is being used: