admin role have the additional responsibility to store important metadata for compression and system configuration. In most cases, an system should have the majority of SQL Nodes assigned to the admin role.
Administrator Node Redundancy
To ensure high availability and consistency, an System must always have a minimum number of operational nodes withadmin privileges.
Redundancy for the system configuration and dictionary compression operates using a majority present model. In a system with N nodes configured with the admin role, at least N / 2 + 1 must be present and active for the system to function correctly, where N is the total number of nodes, and N / 2 denotes the division floor (i.e., rounded down to the nearest integer).
This table shows the number of nodes with admin privileges that can fail before the system experiences problems. Both columns comprise only nodes assigned the admin role, not the entire system node count.
| Number of Nodes | Node Failures Tolerated |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 2 |
| 6 | 2 |
| 7 | 3 |
The majority present model for nodes with the
admin role is different than parity encoding used for Foundation Nodes.For details on parity width for Foundation Nodes, see Configure Storage Spaces.Administrator Node Metadata
This table describes additional metadata files stored by nodes running theadmin role. If you remove the admin role from a node, the system removes these files.
| File path | Description |
|---|---|
/var/opt/ocient/metadataStorage.raft | Definitions for users, network configuration, and database objects. |
/var/opt/ocient/globalDataStorage.raft | Compression dictionaries for the COMPRESSION GDC columns. |
Configure Nodes with the Administrator Role
To configure a node to run theadmin role, execute this SQL statement.
SQL
admin role. You can configure additional nodes with the admin role to adjust the level of redundancy to your chosen level.