The Oracle Active Session History (ASH) - a real treasure trove

When Oracle introduced the Active Session History (ASH) a new gate of tuning and monitoring options was opened.  Yes we had statspack, extended tracing and so on but all these tools were mssing a time(line) dimension. For example statspack reports and later AWR reports are flattened aggregations of numbers carefully to interpret as details are flushed as you always have only a look on an aggregated view of performance metrics.

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Yet another workaround for missing AVG() function for the Oracle interval type

Isn't it similar to you experience with Oracle SQL? there are a few places in the Oracle SQL implementation where you think why didn't they think it through to the end or did they only partially implement a feature?

So you are not the only one suffering from this. It does not mean Oracle SQL is inconsistent as it is indeed a mighty mature tool to handle date and structures in the Oracle database.

Coming to the point:

There are max()/min() functions defined for the interval Oracle data type but not an average avg() function. This means if you want a consistent output, same data type and precision you have to work around a bit and grab into the tool set of SQL to emulate this missing functionality.

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dramatic differences of in memory scanning performance on range queries

Given following two identical tables, on which run the same SQL,  replicated in memory with oracle in-memory option - one table created out of the other.
each tables covers 24m rows.
Same structure ...

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Why the In-Memory Column Store is not used (II)

Now after some research - I detected one simple rule for provoking In-Memory scans :

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Why the In-Memory Column Store is not used (I)


Now finally after a long period of waiting - and looking presentations and reading blogs I was able to do In-Memory databasing on my own. Having sampled some theoretical background how a a pure In-Memory Db works with SAP HANA; my expectations on the Oracle In-Memory Option were high. Also because Oracle promised it would work without code change, out of the box.

The setup

The Oracle database is located on Sun Solaris Machine with enough memory and 32 Xeon-Cores; The Memory Pool is sized 64G, compared to the rest of the SGA , buffer cache , shared_pool ... 4G, and 300G of data.

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