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## 10.4. Upgrading

A database can be upgraded from a minor version to the next, e.g. 1.1 → 1.2, and 1.2 → 1.3, but you can not jump directly from 1.1 → 1.3. The upgrade process is a one way step; databases cannot be downgraded.

For most upgrades, only small changes are required to the database store, and these changes proceed automatically when you start up the database using the newer version of Neo4J.

However, some upgrades require more significant changes to the database store. In these cases, Neo4j will refuse to start without explicit configuration to allow the upgrade.

The table below lists recent Neo4J versions, and the type of upgrade required.

Upgrade process for Neo4J version

From Version | To Version | Upgrade Type
--- | --- | ---
1.3 | 1.4 | Automatic
1.4 | 1.5 | Explicit

### 10.4.1. Automatic Upgrade

To perform a normal upgrade (for minor changes to the database store):

1. download the newer version of Neo4j
2. cleanly shutdown the database to upgrade, if it is running
3. startup the database with the newer version of Neo4j

### 10.4.2. Explicit Upgrade

To perform a special upgrade (for significant changes to the database store):

1. make sure the database you are upgrading has been cleanly shut down
2. set the Neo4j configuration parameter "allow_store_upgrade=true" in your `neo4j.properties` or embedded configuration
3. start the database
4. the upgrade will happen during startup and the process is done when the database has been successfully started
5. "allow_store_upgrade=true" configuration parameter should be removed, set to "false" or commented out

### 10.4.3. Upgrade 1.4 → 1.5

This upgrade includes a significant change to the layout of property store files, which reduces their size on disk, and improves IO performance. To achieve this layout change, the upgrade process takes some time to process the whole of the existing database. You should budget for several minutes per gigabyte of data as part of your upgrade planning.

In an HA environment these steps need to be performed:

1. shut down all the databases in the cluster
2. shut down the zoo keeper cluster and clear the `version-2` directories on all the zoo keeper instances
3. start the zoo keeper cluster again
4. remove the databases except the master and start the master database with 1.5, where migration will happen
5. start up the other databases so that they get a copy from the master

| Warning
The upgrade process for this upgrade temporarily requires additional disk space, for the period while the upgrade is in progress. Before starting the upgrade to Neo4J 1.5, you should ensure that the machine performing the upgrade has free space equal to the current size of of the database on disk. You can find the current space occupied by the database by inspecting the store file directory (`data/graph.db` is the default location in Neo4J server). Once the upgrade is complete, this additional space is no longer required.

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