OTN Appreciation Day: Automatic Storage Management (ASM)

Big shout out to Tim for kicking this off!

Automatic Storage Management (ASM) provides optimised volume management and filesystem capabilities for Oracle databases, whether they be single or multi instance (RAC) implementations.

Although introduced with Oracle 10g Release 1 in 2004, I first used it in a production scenario around 2008, when upgrading a hardware platform for a Data Warehouse. It seemed like a logical choice for myself and the DBAs at the time, although the storage team were less pleased at losing some control. Ultimately it proved a big success on that project and is still in stable, reliable use today.

Things I like about ASM include:

  • Simplifies storage management
  • Automatic rebalancing when capacity is added
  • Visibility within Enterprise Manager for monitoring
  • Availability of detailed metrics within the database
  • Reliable, balanced and consistent performance
  • Works with RAC
  • Rolling upgrades and patching
  • Provides a reliable cluster filesystem (ACFS)
  • Even more cool features coming in 12c such as Flex ASM

 

Some useful links:

ASM Administrators Guide 12cR1 (Oracle Docs)

The Mother Of All ASM Scripts (John Hallas)

Technical overview of new features for ASM in 12c (Whitepaper)

“Unstructured Data” – No such thing!

I keep hearing this term lately and I dislike it.

There is no such thing as Unstructured Data. All data has structure. If it didn’t have structure we wouldn’t be able to use it.

What about free text? Well, that’s just a single column value (stored in a CLOB in Oracle, for example) and the free text is, more often than not, on a row with other columns, such as identifiers and timestamps, i.e. yet more structure.

I think what people mean when they use this “marketing foam”TM term is “data that we have not yet defined the structure for”, but in order to use it at some later stage, the structure will need to be defined – that definition process doesn’t actually give the data structure in and of itself, it simply defines what that structure is, in order to be able to use it.

Interestingly, the Wikipedia article for Unstructured Data calls out the imprecise nature of the term:

The term is imprecise for several reasons:

  1. Structure, while not formally defined, can still be implied.
  2. Data with some form of structure may still be characterized as unstructured if its structure is not helpful for the processing task at hand.
  3. Unstructured information might have some structure (semi-structured) or even be highly structured but in ways that are unanticipated or unannounced.

In other words, it does have structure, but maybe we’ve not written it down, or the structure isn’t helpful to processing or is structured in ways we were not expecting – so what?…it’s still structured!

All of the above seem to me to support the view that all data does indeed have structure.