TECHNICAL FIELD

The present disclosure relates to networked storage systems and more particularly to, cloning a tenant database from a backup copy of a multitenant database.

BACKGROUND

Various forms of storage systems are used today. These forms include direct attached storage (DAS) systems, network attached storage (NAS) systems, storage area networks (SANs), and others. Network storage systems are commonly used for a variety of purposes, such as providing multiple users with access to shared data, backing up data and others. A storage system typically includes at least one computing system executing a storage operating system for storing and retrieving data on behalf of one or more client computing systems (“clients”). The storage operating system stores and manages shared data containers in a set of mass storage devices. Storage systems are used by different applications, for example, multitenant database systems, electronic mail (email) servers, virtual machines executed within virtual machine environments (for example, a hypervisor operating environment) and others to store and protect data using backups.

A multitenant database system enables a plurality of independent tenant databases to store information using a single database container (or instance). An example of a multitenant database system is provided by Oracle Corporation (without derogation of any trademark rights). The multitenant database system has a container database (CDB) as a “master database”, to enable access to a plurality of tenant databases, may also be referred to as “pluggable databases (“PDBs”)”, throughout this specification. The CDB is typically presented by a computing device (also referred to as a host system) or within a virtual machine hosted by the computing device. The CDB operates as an independent logical entity to store configuration information regarding each PDB. The PDBs operate as independent databases to store data. The CDB and the PDBs may be protected by taking point in time backups (also referred to as “snapshots”) by the storage system.

Conventional database providers and storage systems may store backups of CDBs and PDBs, but typically, fail to efficiently enable cloning a specific PDB from a backup copy of a source CDB and present the PDB clone at a target CDB that may be hosted at a different or same host system as the source CDB. For example, Oracle Corporation provides a limited option for taking snapshot of a PDB only for Network File System (NFS) and Oracle Automatic Storage Management Cluster File System (Oracle ACFS) but not for Storage Area Network (SAN) file systems that are extensively used by storage systems. Furthermore, if one wants to clone the PDB from the snapshot, then the source PDB must remain a read-only snapshot during the lifetime of the PDB clone. This limitation is undesirable because it limits a user's ability to use the source PDB as a read-write PDB. The Oracle Corporation solution also requires that the PDB can only be cloned when the source CDB is shutdown, and the PDB clone can only be hosted on the same host system that hosts the source CDB. This limits a user's ability to use a PDB clone on an alternate host without affecting the source CDB or the source CDB host. Continuous efforts are being made to develop computing technology to efficiently use a source CDB backup taken by a storage system to enable cloning a PDB from the source CDB backup, and then present the PDB clone on a target CDB hosted by a different host computing device or the same device as the source CDB. It is also desirable that the storage system efficiently manage the overall life cycle of the PDB clone regardless of whether the source CDB is operational or shutdown. It is also desirable that the PDB cloning process to be storage space efficient and can be performed without having to copy PDB files from the source CDB backup to the PDB clone.

