VDB Versioning is a feature that allows multiple versions of a VDB to be deployed at the same time with additional support to determine which version will be used. When a user connects to Teiid the desired VDB version can be set as a connection property (See the Client Developer's Guide). If a specific version is set, then only that VDB may be connected to. If no version is set, then the deployed VDBs are searched for the appropriate version. This feature helps support more fluid migration scenarios.
Setting the version can either be done in the vdb.xml, which is useful for dynamic vdbs, or through a naming convention of the deployment file - vdbname.version.vdb, e.g. marketdata.2.vdb. The deployer is responsible for choosing an appropriate version number. If there is already a VDB name/version that matches the current deployment, then connections to the previous VDB will be terminated and its cache entries will be flushed. Any new connections will then be made to the new VDB.
Once deployed a VDB has an updatable property called connection type, which is used to determine what connections can be made to the VDB. The connection type can be one of:
NONE- disallow new connections.
BY_VERSION- the default setting. Allow connections only if the version is specified or if this is the earliest BY_VERSION vdb and there are no vdbs marked as ANY.
ANY- allow connections with or without a version specified.
The connection type may be changed either through the AdminConsole or the AdminAPI.
If only a select few applications are to migrate to the new VDB version, then a freshly deployed VDB would be left as BY_VERSION. This ensures that only applications that know the new version may use it.
If only a select few applications are to remain on the current VDB version, then their connection settings would need to be updated to reference the current VDB by its version. Then the newly deployed vdb would have its connection type set to ANY, which allows all new connections to be made against the newer version. If a rollback is needed in this scenario, then the newly deployed vdb would have its connection type set to NONE or BY_VERSION accordingly.