Hive table definitions, mappings and other metadata are stored in Metastore. This can be stored in a RDBMS supported by JPOX.
By default only one user can see Metastore at a time.
Metastore has two parts.
1. Metastore Service: This service provides interface between Hive and users/processed.
2. Metastore Database: This database stores table definitions, data mappings etc.
In default configuration, Hive Metastore is stored in same JVM as Hive driver. This is also known as Embedded Metastore, which is good for Dev and Testing environments.
We can also use an external DB like MySQL for storing Metadata. This configuration is called Local Metastore.