Synchronizing Metadata

An Eon Mode database maintains its catalog, which contains all database metadata, in communal storage. Vertica uses this metadata when it revives the database, so it is important that the catalog is always up to date. Vertica automatically synchronizes the catalog at regular intervals as specified by the configuration parameter CatalogSyncInterval —by default, set to five minutes.

In general, it is not necessary to monitor the synchronization process or change it. One exception applies: before shutting down a database that you intend to revive or replicate, it is good practice to verify that the catalog contains all recent changes, and if necessary synchronize it manually.

Verifying Catalog Status

You can verify the synchronization status of the database catalog in two ways, depending on whether the database is running.

If the database is running, query and compare these two system tables:

• CATALOG_SYNC_STATE: Shows how recently each node synchronized its catalog to communal storage, and the version that it synchronized.
• CATALOG_TRUNCATION_STATUS: Shows the latest synchronization status of the database catalog. Catalog synchronization is up to date when columns TRUNCATION_CATALOG_VERSION and CURRENT_CATALOG_VERSION are the same.

If the database is not currently running, check the following JSON file on communal storage:

/metadata/database‑name/cluster_config.json

The catalog truncation version and timestamp in this file indicate when Vertica last synchronized the database catalog.

Manually Synchronizing the Database Datalog

If necessary, call SYNC_CATALOG to synchronize the catalog immediately with all nodes or a specific node:

=> SELECT sync_catalog();

Customizing Synchronization Intervals

By default, Vertica checks for catalog changes every five minutes. Occasionally, you might want to change this setting temporarily—for example, set it to a high value in order to take a snapshot of the current bucket contents:

=> ALTER DATABASE DEFAULT SET CatalogSyncInterval = 300;

=> ALTER DATABASE DEFAULT CLEAR PARAMETER CatalogSyncInterval;