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Table Of Contents

Chapter 13

Estimating Memory Requirements

Designing a SQLFire database also involves estimating the memory requirements for your data based on the size of

the actual table values and indexes, the overhead that SQLFire requires for your data, and the overall usage pattern for

your data. You can estimate the memory requirements for tables using general guidelines for SQLFire overhead. Or,

you can load tables with representative data and then query the SQLFire SYS.MEMORYANALYTICS table to obtain

details about the memory required for individual tables and indexes.

Estimating SQLFire Overhead

SQLFire requires different amounts of overhead per table and index entry depending on whether you persist

table data or conﬁgure tables for overﬂow to disk. Add these overhead ﬁgures to the estimated size of each table

or index entry to provide a rough estimate for your data memory requirements. If you already have representative

data, use the SQLFire Java agent to query the SYS.MEMORYANALYTICS table to obtain a more accurate

picture of the memory required to store your data.

Note: All overhead values are approximate. Be sure to validate your estimates in a test environment with

representative data.

Table 1: Approximate Overhead for SQLFire Table Entries

Approximate overheadOverflow is configured?Table is persisted?

64 bytesNoNo

120 bytesNoYes

152 bytesYesYes

Table 2: Approximate Overhead for SQLFire Index Entries

Approximate overheadType of index entry

80 bytesNew index entry

24 bytesFirst non-unique index entry

8 bytes to 24 bytes*Subsequent non-unique index entry

*If there are more than 100 entries for a single index entry, the overhead per entry increases from 8 bytes to

approximately 24 bytes.