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Showing posts from November, 2016

Clarify myths of indexing foreign key constraints on Oracle-DB

If you use foreign keys there’s one very common dogma: You always need to index all the column(s) for which you define a foreign key constraint! I definitely do not agree with this dogma and want to explain why. There are two reasons for indexing columns with foreign key constraints: Avoiding full table scans on referencing table during deletes on referenced tables  Avoiding blocking lock problems e.g. if you are doing DML on both referencing and referenced table  You may find a detailed description of the locking behaviour of foreign keys at chapter "Locks and Foreign Keys" here in the Oracle documentation . Considerations on full table scan due to foreign key constraint not protected by index If you do not index referencing column(s) than delete on referenced table leads to a full table scan on referencing table for every deleted row  Therefore you should index referencing column(s) especially in OLTP-environments if your referenced table has more than a small

Panorama: Save request parameter to recall page with specific filters at later time

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Sometimes in Panorama you have drilled down in analysis from step to step, cumulated several filter conditions and found what you are looking for. This finding you want to share with colleagues or store for later use. Panorama allows you at several pages to copy your current request parameter to clipboard and use ist later to reconstruct your current page. Saving request parameters: Choose “Copy request parameters to clipboard” from small menu at left corner of headline (if it is available for this function). You can use parameters from clipboard now to store or mail or … Restore a page with given parameters: Call menu “Spec. additions / Execute with given parameters” and paste your stored parameters in text area. Click execute to restore your page with this parameters.