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# mapdb Persistence v1
The mapdb (opens new window) Persistence Service is based on simple key-value store that only saves the last value. The intention is to use this for restoreOnStartup items because all other persistence options have their drawbacks if values are only needed for reload. They:
- grow in time
- require complex installs (
mysql,influxdb, ...) rrd4jcan't store all item types (only numeric types)
Querying the mapdb persistence service for historic values other than the last value make no sense since the persistence service can only store one value per item.
# Configuration
This service can be configured in the file services/mapdb.cfg.
| Property | Default | Required | Description |
|---|---|---|---|
| commitinterval | 5 | No | commit interval in seconds |
| commitsamestate | false | No | set to true to issue a commit even if the state did not change |
All item and event related configuration is done in the file persistence/mapdb.persist.
To configure this service as the default persistence service for openHAB 2, add or change the line
org.eclipse.smarthome.persistence:default=mapdb
in the file services/runtime.cfg.
# Troubleshooting
Restore of items after startup is taking some time. Rules are already started in parallel. Especially in rules that are started via System started trigger, it may happen that the restore is not completed resulting in undefined items. In these cases the use of restored items has to be delayed by a couple of seconds. This delay has to be determined experimentally.