[ http://issues.apache.org/jira/browse/DERBY-271?page=all ]
Jeff Levitt reassigned DERBY-271:
---------------------------------
Assign To: Jeff Levitt
> Document the new property derby.system.durability=test
> ------------------------------------------------------
>
> Key: DERBY-271
> URL: http://issues.apache.org/jira/browse/DERBY-271
> Project: Derby
> Type: Sub-task
> Components: Documentation
> Versions: 10.1.0.0
> Reporter: Sunitha Kambhampati
> Assignee: Jeff Levitt
>
> Need to document the new property - derby.system.durability
> This should probably go along with other properties in Tuning guide.
> --------------------------------------------------
> derby.system.durability
> Currently the only valid supported case insensitive value is 'test'
> If this property is set to any other value other than 'test', this
> property setting is ignored
> In the future, this property can be used to set different modes of durability
> - for example a form of relaxed durability where database can recover to a
> consistent state, or to enable some kind of in-memory mode.
> When set to 'test', the store system will not force sync calls in the
> following cases
> - for the log file at each commit
> - for the log file before data page is forced to disk
> - for page allocation when file is grown
> - for data writes during checkpoint
> That means
> - a commit no longer guarantees that the transaction's modification
> will survive a system crash or JVM termination
> - the database may not recover successfully upon restart
> - a near full disk at runtime may cause unexpected errors
> - database can be in an inconsistent state
> This setting is provided for performance reasons and should ideally
> only be used when the system can withstand the above consequences.
> One sample use would be to use this mode (derby.system.durability=test)
> when using Derby as a test database, where high performance is required
> and the data is not very important.
> If database is booted with derby.system.durability=test, the following
> warning message is logged in derby.log
> WARNING: The database is booted with derby.system.durability=test. In this
> mode, it is possible that database may not be able to recover, committed
> transactions may be lost, database may be in an inconsistent state. Please
> use this mode only when these consequences are acceptable
> and a similar message will appear in derby.log if the database was booted
> with derby.system.durability=test at any time previously.
> It is important to realize that once the database is booted with
> derby.system.durability=test, there are no guarantees on if the database is
> consistent or not.
> -------------------
> Valid supported values are test
> Example
> derby.system.durability=test
> One can set this as a command line option to the JVM when starting the
> application or in the derby.properties file. It is a system level
> property.
> This property is static; if you change it while Derby is running,
> the change does not take effect until you reboot.
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