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Add docs for journal compaction startup options

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Martin Sumner 2018-07-23 13:59:24 +01:00
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docs/STARTUP_OPTIONS.md
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@ -70,3 +70,13 @@ Compression point can be set using `{compression_point, on_receipt|on_compact}`.
## Root Path
The root path is the name of the folder in which the database has been (or should be) persisted.
## Journal Compaction
The compaction of the Journal, is the process through which the space of replaced (or deleted) objects can be reclaimed from the journal. This is controlled through the following parameters:
The `compaction_runs_perday` indicates for the leveled store how many times eahc day it will attempt to run a compaction (it is normal for this to be ~= the numbe rof hours per day that compcation is permitted).
The `compaction_low_hour` and `compaction_high_hour` are the hours of the day which support the compaction window - set to 0 and 23 respectively if compaction is required to be a continuous process.
The `max_run_length` controls how many files can be compacted in a single compaction run. The scoring of files and runs is controlled through `maxrunlength_compactionpercentage` and `singlefile_compactionpercentage`.