Blog: Jonathan Lewis

210 blogs updated: 13 min. ago
exp catch
No-one should be using exp/imp to export and import data any more, they should be using the datapump equivalents expdp/impdp but if you're o...
10-04-2018 19:58:07 Jonathan Lewis Oracle
Data Hashing
Here's a little-known feature that has been around since at least Oracle 10, though I don't think I had ever seen it in the wild until today...
09-04-2018 19:54:46 Jonathan Lewis Oracle
SQL Monitor
I've mentioned the SQL Monitor report from time to time as a very useful way of reviewing execution plans the feature is automatically enabl...
06-04-2018 09:43:54 Jonathan Lewis Oracle
Lock Types
Every now and again I have to check what a particular lock (or enqueue) type is for and what the associated parameter values represent. This...
28-03-2018 13:39:12 Jonathan Lewis Oracle
Reference Costs
The partitioning option "partition by reference" is a very convenient option which keeps acquiring more cute little features, such as cascad...
19-03-2018 09:06:42 Jonathan Lewis Oracle
Keeping Intervals
I've recently been reminded of a blog post I wrote a couple of years ago that discussed the issue of running into the hard limit of 2^20 -1 ...
15-03-2018 10:07:25 Jonathan Lewis Oracle
Deferred Invalidation
I was going to write an article on the way 12.2 has introduced the option for "deferred invalidation" for a number of DDL operations, but I ...
13-03-2018 20:47:08 Jonathan Lewis Oracle
Comparing Plans
It can be difficult to find the critical differences when comparing execution plans when you want to find out why the optimizer has changed ...
12-03-2018 09:36:22 Jonathan Lewis Oracle
Column Groups
There's a question on the ODC database forum about column groups that throws up an interesting side point. The OP is looking at a query like...
08-03-2018 07:55:40 Jonathan Lewis Oracle
Match_recognise – 2
In my previous post I presented a warning about the potential cost of sorting and the cost of failing to find a match after each pass of a l...
06-03-2018 10:09:27 Jonathan Lewis Oracle

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