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Optimisation ?
I was at a client site recently where one of the end-users seemed to have discovered a cunning strategy for optimising a critical SQL statement. His problem was that his query screen times out after 2...
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Free Space
Question – How can you have a single file in a single tablespace showing multiple free extents when there are no objects using any space in that file ? For example, from an 11.1.0.7 database: SQL>...
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Oracle x86 Systems – Putting the Infrastructure in IaaS (Part One of Three)
Recent IDC cloud research shows that worldwide revenue from public IT cloud services will reach $72.9 billion in 2015, representing a compound annual growth rate (CAGR) of 27.6%. Specifically,...
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LOB Update
This note is about a feature of LOBs that I first desribed in “Practial Oracle 8i” but have yet to see used in real life. It’s a description of how efficient Oracle can be, which I’ll start with a...
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Open Cursors
Here’s a little detail that appeared in 11gR2 that may help you answer questions about open cursors. Oracle has added a “cursor type” column to the view v$open_cursor, so you can now see which cursors...
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ASM AU Size And LMT AUTOALLOCATE
When using Locally Managed Tablespaces (LMT) with variable, system managed extent sizes (AUTOALLOCATE) and data files residing in ASM the Allocation Unit (AU) size can make a significant difference to...
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MV Refresh
Materialized views open up all sorts of possibilities for making reporting more efficient – but at the same time they can introduce some “interesting” side effects when you start seeing refreshes...
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Hakan Factor
Here’s a quick and dirty script to create a procedure (in the SYS schema – so be careful) to check the Hakan Factor for an object. If you’re not familiar with the Hakan Factor, it’s the value that gets...
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SQL*Net Compression – 2
I wrote a note a few years ago about SQL*Net compression (this will open in a new window so that you can read the posts concurrently), showing how the order of the data returned by a query could affect...
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Wasted Space
Here’s a little quiz: If I take the average row length of the rows in a table, multiply by the number of rows, and convert the result to the equivalent number of blocks, how can the total volume of...
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12c trivia
Weighing in at a massive 54 characters – the longest parameter name in 12c is: _adaptive_scalable_log_writer_disable_worker_threshold Followed very closely by (you guessed it)...
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ASSM
A couple of thoughts. The intent of ASSM is to minimise contention when multiple small transactions are busy inserting data concurrently into the same table. As a consequence, you may be able to find a...
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Manuals
Just glancing through the 12c manuals (Server Reference 12.1 June 2013 – E17615-16) to check a particular database limit, I came across the following: “Services – maximum per instance – 115″. That’s a...
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MV Refresh
Here’s a funny little problem I came across some time ago when setting up some materialized views. I have two tables, orders and order_lines, and I’ve set up materialized view logs for them that allow...
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Sorted Hash Clusters RIP
Sorted Hash Clusters have been around for several years, but I’ve not yet seen them being used, or even investigated in detail. This is a bit of a shame, really, because they seem to be engineered to...
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MV Refresh
I have a fairly strong preference for choosing simple solutions over complex solutions, and using Oracle-supplied packaged over writing custom code – provided the difference in cost THere’(whether...
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Virtual Integrity
A recent question on the Oracle-L list server described a problem with data coming in from SQL Server and an oddity with referential integrity failing on Oracle because (for example) a child row was in...
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Virtual date partitions
I posted this question on twitter earlier on today (It was a thought that crossed my mind during a (terrible) presentation on partitioning that I had to sit through a few weeks ago – it’s always...
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12c In-memory
I wrote a note about the 12c “In-Memory” option some time ago on the OTN Database forum and thought I’d posted a link to it from the blog. If I have I can’t find it now so, to avoid losing it, here’s a...
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Row Movement
Here’s a question that appeared recently on OTN, and it’s one I’ve wondered about a few times – but never spent any time investigating. Are there any overheads to enabling row movement on a table ? If...
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