With the introduction of Exascale, some new software is located on the Exadata database servers.
From an end-user perspective, Oracle Database functionality remains essentially the same. However, the database kernel is modified internally to provide seamless support for Exascale. Instead of using a separate ASM instance, databases on Exascale contain a mapping table in the SGA. This table is a relatively small directory that enables the database to locate the appropriate storage server for any given data. The database instance also contains two new background processes (EGSB and EDSB), which maintain instance-level metadata about the Exascale cluster (otherwise known as Exascale global services or EGS) and Exascale vaults (otherwise known as Exascale data stores or EDS). With Exascale, it is important to note that database clients direct I/O to the appropriate Exadata storage server, not through EGSB or EDSB.
On each Exadata database server, the Exadata System Software also contains new software components, including:
- The Exascale Command-Line Interface (ESCLI) is a command-line administration tool available on Exadata database and storage servers. You can use ESCLI to perform Exascale monitoring and management functions. ESCLI compliments the existing Exadata command-line interfaces (DBMCLI and CellCLI) and does not replace them.
The Exascale node proxy (ESNP) service maintains information about the current state of the Exascale cluster, which it provides to local Oracle Grid Infrastructure and Oracle Database processes.
The Exascale Direct Volume (EDV) service exposes Exascale block storage as raw block devices on Exadata compute nodes. EDV-managed storage can be used as raw storage devices or to support various file systems, including Oracle Advanced Cluster File System (ACFS). This service is required on all Exadata compute nodes where you want to use EDV devices.
Exascale cluster services, also known as Exascale global services (EGS), provide the core foundation for the Exascale system. For high availability, EGS runs in a cluster of five service instances. Each EGS instance typically runs on an Exadata storage server. However, for Exadata configurations with fewer than five storage servers, EGS instances run on the Exadata database servers to make up the required number.
Oracle Grid Infrastructure continues to provide cluster services for Exadata databases. However, databases that use Exascale storage do not require an ASM instance.