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1 Reply Latest reply: Dec 8, 2011 7:34 AM by Paula B RSS

Calculating the size of the database in memory

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I am using BDB 5.1.19 with BTREE as an access method.
I would like to calculate the memory footprint that would be needed for that.
I followed the following doc:

useful-bytes-per-page = (page-size - page-overhead) * page-fill-factor
bytes-of-data = n-records *
(bytes-per-entry + page-overhead-for-two-entries)
n-pages-of-data = bytes-of-data / useful-bytes-per-page
total-bytes-on-disk = n-pages-of-data * page-size

I am not interested in calculating the size on disk but just in memory.
Would the following be enough:
bytes-of-data = n-records *(bytes-per-entry + page-overhead-for-two-entries)

Since the rest is only for space on disk i don't need it, is that correct?
Would this calculation help me also to calculate the cache size or is the cache size influenced by the page size?



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