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Hi Rob,

there is very little overhead for DD entries over all , let mesee if I can dig up my rough sizing calculations.

The base overhead for the Data Dictionary Cache is as follows:

X1 = 24 + (40 * DD_HASHSIZE)

Below is the minimum cost of every Data Dictionary entry:

Y1 = 352 + (96 * Number of Columns per table)


Total size (rough estimate)

TS = X1 + (Y1 * (DD_HASHSIZE * DD_HASHMAX))

(Please note that Total size is not really as easy as the above,
because of two primary factors, the first is that Y1 is only for an individual entry, which is highly unlikely to represent the median of all entries, and the second is the pools can actually grow beyond DD_HASHSIZE for a short period of time)



Currently my recommendations for the DD caches id to setDD_HASHSIZE to the prime number closest to the number of unique user created tables, obviously with Baan I believe you may want to cut that a little short. DD_HASHMAX by default is 10 and should be left that way, the deeper your pool the less efficient it is.. I've worked with DD_HASHSIZE set to close to the value you list below, however not quite that high. The amount ofvirtual memory that actually gets added is not that big.

Even if you go with

DD_HASHSIZE 20101
DD_HASHMAX 10

I would monitor your DD cache, onstat -g dic, to see if you have pools that areconsistantly larger than 10, if so I would continue to bump DD_HASHSIZE upto the next prime number.




----- Original Message ----
From: RoB <plumas4u@yahoo.com>
To: informix-list@iiug.org
Sent: Wednesday, November 1, 2006 9:01:13 AM
Subject: DD_HASHSIZE/MAX on a Baan installation with more than 100, 000 tables.


Hi all,

OS: HP-UX 11.11
IDS: 7.31.FD8

Question: Would it be insane to set these parameters to values as below
for an IDS instance used by Baan with more than 100,000 tables?

DD_HASHSIZE 20101
DD_HASHMAX 5

Has anyone had any experience with setting DD_HASHSIZE to a value this
high? What would be the implications (memory usage etc)? Are there any
other recommendations?

RoB

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