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Berkeley DB Reference Guide: Programmer Notes



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Database limits



NThe largest database file that Berkeley DB can handle depends on the page sizeNselected by the application. Berkeley DB stores database file page numbers asGunsigned 32-bit numbers and database file page sizes as unsigned 16-bitHnumbers. Using the maximum database page size of 65536, this results inDa maximum database file size of 248 (256 petabytes). TheCminimum database page size is 512 bytes, which results in a minimum6maximum database size of 241 (2 terabytes).

PThe largest database file Berkeley DB can support is potentially further limitedIif the host system does not have filesystem support for files larger thanH232, including the ability to seek to absolute offsets within those files.

MThe largest key or data items that Berkeley DB can support is largely limitedGby available memory. Specifically, while key and data byte strings mayAbe of essentially unlimited length, any one of them must fit intoHavailable memory so that it can be returned to the application. As somePof the Berkeley DB interfaces return both key and data items to the application,Gthose interfaces will require that any key/data pair fit simultaneouslyHinto memory. Further, as the access methods may need to compare key andFdata items with other key and data items, it may be a requirement thatGany two key or two data items fit into available memory. Finally, whenIwriting applications supporting transactions, it may be necessary to haveCan additional copy of any data item in memory for logging purposes.

The maximum btree depth is 255.

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