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Secondary index without MANDT field.

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Secondary index without MANDT field.

Postby DrSidewalk » Tue Nov 26, 2013 7:30 am

I have seen a few customer secondary indicies containing no MANDT field.

I feel sure this will affect the effeciency of any SQL using this index, but can't be sure.
What's the Basis stance on this, I wonder?.

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Re: Secondary index without MANDT field.

Postby hoinz » Tue Nov 26, 2013 10:32 am

As usually, it depends.
But I dare say: In most cases it doesn't matter.
There seems to be kind of 'good practice' to have MANDT included, but that's all about it.

Let's assume you have one productive client, let's say 100, and let's say table XXX has a few million entries, and 99 percent or more of them belong to client 100. Now if you are searching for some entries in client 100, there will be no sensible difference, whether or not the client/mandt is part of the index.
On the other hand, in one of the rare cases where you are looking for entries in client 001, there will be a sensible difference.

regards
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Re: Secondary index without MANDT field.

Postby Snowy » Tue Nov 26, 2013 3:58 pm

with DB2 v10, it is possible to use a part of an index. so, from this point, the MANDT field might be of minimum use.
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Re: Secondary index without MANDT field.

Postby blueteeth » Tue Apr 08, 2014 1:47 pm

It's my usual grouse on secondary indexes.

While secondary indexes hasten fetch (read) queries, they have their overhead on frequently updated tables. Please remember, every DML statement (data manipulation language) like update, modify or delete will impact its indexes. A corresponding i/o activity takes place in indexes. Over time, they also become fragmented.

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Re: Secondary index without MANDT field.

Postby Zavaros » Wed Apr 09, 2014 10:57 am

Hello,

it all depends on the select command.

I was taught that the SAP kernel inserts mandt field to all select commands when the mandt field is present in the table.

Nevertheless we have lot of secondary indices without mandnt field that were advised by ADDM and other tools.

Regards,

Zav

PS: ... oops ... it is a revived topic!
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