[ http://issues.apache.org/jira/browse/DERBY-271?page=comments#action_65635 ] Sunitha Kambhampati commented on DERBY-271: -------------------------------------------
It looks good to me now. > 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 > Attachments: derby271modifiedfinal.zip > > 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. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
