Globally Distributed Exadata Database on Exascale Infrastructure (Distributed ExaDB-XS) brings the power of sharded databases to Oracle Exadata Database on Exascale Infrastructure.

Distributed ExaDB-XS is a cloud-based, fully-managed database service that enables the sharding of data across globally distributed converged databases. It is designed to support large-scale, mission-critical applications. It is a highly available, fault-tolerant, and scalable database service that enables organizations to store and process massive amounts of data with high performance and reliability.

The Distributed ExaDB-XS is built on top of Oracle's Exascale software services technology, which further empowers Exadata to meet the most demanding corporate and cloud computing requirements by decoupling Oracle Database and GI clusters from the underlying Exadata storage servers. Exascale software services can manage a large fleet of Exadata storage servers connected by the Exadata RDMA Network Fabric, providing storage services to multiple GI clusters and databases while enabling:

• Secure sharing of storage resources with strict data isolation, allowing different users and databases to share a large pool of storage while ensuring that data is inaccessible to users without the appropriate privileges

• Flexible and dynamic storage provisioning for many users and databases

• Increased storage utilization and efficiency while reducing storage costs

• Sharing of otherwise idle storage processing resources to improve performance

For more information about Oracle Exadata Exascale on Oracle Cloud, see Oracle Cloud Exadata Database Service on Exascale Infrastructure .

For a detailed discussion of sharded database features, see Oracle Globally Distributed Database Overview for Oracle Database 23ai.

To gain a greater understanding of Globally Distributed Database concepts, familiarize yourself with the following terminology.

• Catalog - an Oracle Database that supports automated shard deployment, centralized management of the distributed database, and multi-shard queries.

  A Catalog serves following purposes:

  • Serves as an administrative server for the entire distributed database

  • Stores a gold copy of the database schema

  • Manages multi-shard queries with a multi-shard query coordinator

  • Stores a gold copy of duplicated table data

• Shard - A distributed database is a collection of shards.

  Each shard in a distributed database is an independent Oracle Database instance that hosts subset of the distributed database data. Shared storage is not required across the shards.

  Shards can all be placed in one region or can be placed in different regions.

  Shards are replicated for high availability and disaster recovery with Oracle Data Guard. For high availability, Data Guard standby shards can be placed in the same region where the primary shards are placed. For disaster recovery, the standby shards can be located in another region.

• Shardspace - A shardspace is a shard that stores data corresponding to a range or list of key values in a user-managed data distribution configuration. A shardspace consists of a shard and its replica.

• Shard director - A network listener that enable high performance connection routing based on a sharding key. In addition, a shard director is a set of processes known collectively as a Global Service Manager (GSM) that acts as a regional listener for clients that connect to a Globally Distributed Database.

  The shard director maintains a current topology map of the distributed database. Based on the sharding key passed during a connection request, the director routes the connections to the appropriate shard.

• Global service - A database service that is used to access data in the distributed database.

  A global service is an extension to the notion of the traditional database service. All of the properties of traditional database services are supported for global services.

For more in depth information about distributed database components and schema objects see Architecture and Concepts in Oracle Globally Distributed Database.

Exadata Database Service on Exascale Infrastructure (ExaDB-XS) provides a cloud service experience similar to Exadata Database Service on Dedicated Infrastructure. You can start with a small virtual machine (VM) cluster, and easily scale as needs grow. Oracle manages all of the physical infrastructure in a shared multitenancy infrastructure service model. Exascale is the underlying technology that serves as the foundation for this service.

Storage for database files resides in an Oracle Exadata Exascale Storage Vault. The Storage Vault provides high performance and scalable Exadata smart storage. Storage can be scaled online as needed, with a single command, and that storage becomes available for immediate use. Unlike Dedicated Infrastructure Exadata Database Service on Exascale Infrastructure does not require you to manage adding storage servers to the system, or manage storage allocations.

The architecture consists of the following elements:

1. A single Exascale Vault, which provides storage for the databases
2. A set of VMs run on Oracle-managed multitenant physical database servers
3. VM filesystems, which are centrally hosted by Oracle
4. A virtual client network (VCN), which provides client and backup network connectivity

Oracle's Globally Distributed Database services offer data replication solutions to ensure high availability, disaster recovery, and additional scalability for reads.

Globally Distributed Exadata Database on Exascale Infrastructure (Distributed ExaDB-XS) offers catalog replication with Oracle Data Guard. Raft replication is available for the shards.

Distributed ExaDB-XS automatically deploys the specified replication topology to the procured systems, and enables data replication.

Catalog Replication with Oracle Data Guard

The catalog is a database. Oracle Data Guard replication to a physical standby databases can be used to provide high availability. Replication is automatically configured and deployed when the sharded database is created.

Oracle Data Guard is tightly integrated with Distributed ExaDB-XS to provide high availability and disaster recovery with strict data consistency and zero data loss. Oracle Data Guard replication maintains a synchronized copy (standby database) of the catalog (the primary database) for high availability and data protection. A standby can be deployed locally or remotely.

Chunk Set-level Replication with Raft Replication

Instead of replication at the whole shard level using additional databases for standbys, the Raft replication feature in a Distributed ExaDB-XS creates sets of chunks of data from each shard and distributes them automatically among the shards to handle chunk assignment, chunk movement, workload distribution, and balancing upon scaling (addition or removal of shards), including planned or unplanned shard availability changes.

Raft replication is built into the Distributed ExaDB-XS to provide a consensus-based, high-performance, low-overhead availability solution, with distributed replicas and fast failover with zero data loss, while automatically maintaining the replication factor if shards fail. With Raft replication management overhead does not increase with the number of shards. If you are used to NoSQL databases and do not expect to know anything about how replication works, native replication just works.

Unlike Data Guard replication, Raft replication does not need to be reconfigured when shards are added or removed, and replicas do not need to be actively managed.

For more details about how Raft replication works see Using Raft Replication in Oracle Globally Distributed Database.

Oracle's Globally Distributed Database services resources have a unique, Oracle-assigned identifier called an Oracle Cloud ID (OCID).

Distributed database resources are listed in the following table.

For example, the OCID format for osddistributeddb is ocid1.osddistributeddb.oc1.iad.<UNIQUE ID>.

For information about the OCID format and other ways to identify your resources, see Resource Identifiers.

Metering and billing for Globally Distributed Exadata Database on Exascale Infrastructure is based on the number of ECPU per hour.

Because Globally Distributed Exadata Database on Exascale Infrastructure provisions Oracle Exadata Database Service on Exascale Infrastructure virtual machine (VM) clusters, billing and metering is handled by Oracle Exadata Database Service on Exascale Infrastructure usage. However, the cluster will be billed under the Globally Distributed Database SKU. See Metering Frequency and Per-Second Billingfor details.

Service Limits specific to Globally Distributed Exadata Database on Exascale Infrastructure can be set for Distributed Database Count and Distributed Database Private Endpoint Count.

Exadata Database virtual machine instances, ECPU count, and storage need to have limits set for the Oracle Exadata Database Service on Exascale Infrastructure (ExaDB-XS).

To understand the resource capacity of the ExaDB-XS service, see Capacity Limits for Exadata Database Service on Exascale Infrastructure.

Oracle's Globally Distributed Database services are integrated with various Oracle Cloud Infrastructure services and features.

• IAM
  
• Work Requests
  
• Monitoring