How big is yours?

Ed Griffiths edgrif at sanger.ac.uk
Wed Jun 21 04:38:37 EST 2000


> What are the largest ace databases that people have worked with (in either
> size Mb (or even Gb), or number of objects) and have people found any
> performance problems with very large databases (obviously this is
> dependent on the computer hosting and accessing the database).
> 
> Are there any theoretical limits on the number of objects an ace db could
> hold?

This is, unfortunately, a "how long is a piece of string" like question. The
number of objects you can stuff into an ace database will be dependent on the
size of those objects. I'm sure you can appreciate that the size can be just
about anything (allowing for various bits of house-keeping information that
every object stored will need). If you mean "can I have a really large number of
objects ?", then the answer is yes, you are likely to run out of disk space
before acedb runs out of index space.

In terms of performance, again its a bit tricky to be specific, there are two
pathological extremes:

	- if you have very big objects in your database then they will take a long time
to load and use up lots of memory.

	- if you have lots of tiny objects and want to search through them all without
using acedbs indexes, then each object must be loaded and explored and again
this will lead to poor performance.

Most databases sit in between these two and acedbs indexing allows many queries
to be done without the need to load objects and look through them, thus giving
very good query performance.

In terms of how big a database can get, well this is (as far as we know) only
dependent on the biggest file size that can be supported by a system. The file
position is usually given by a "long" which could mean anything from a 32 to a
64 bit signed integer. This implies that EACH of the database blockN.wrm files
could be huge. In practice operating systems usually only allow file sizes
somewhat smaller than the theoretical maximum allowed by the file position size.
Its unlikely that this is going to present problems at the moment.

hope this helps a bit...Ed

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| Ed Griffiths, Informatics Group,                                             |
|               The Sanger Centre, Wellcome Trust Genome Campus,               |
|               Hinxton, Cambridge CB10 1SA, UK                                |
|                                                                              |
| email: edgrif at sanger.ac.uk      URL: http://www.sanger.ac.uk/Users/edgrif    |
|   Tel: +44-1223-494780 (switch  +44 1223 834244) Fax: +44 1223 494919        |
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