This topic provides background information about caching system views and describes how to cache them.
Background information
When you migrate data from a large number of tables in OceanBase Database V3.x to OceanBase Database V4.x, the major system views in information_schema, such as STATISTICS, TABLES, and COLUMNS, have no indexes in OceanBase Database V3.x. Each query therefore triggers a full table scan. Schema migration and full migration use these views extensively, and many queries must be run once for every table. As a result, the data migration task may fail to be created.
To address this issue, OceanBase Migration Service (OMS) Community Edition V4.2.5 supports locally caching the system metadata views used in OceanBase Database V3.x. You can create a data migration task after caching the system views, and OMS Community Edition automatically uses the cached data. After the cache is created, the root directory of the local cache files is /home/ds/run/sysmetacache/{endpointId}.
Limits
Currently, system views can be cached only for OceanBase Database V3.x.
Procedure
Click More Actions > Cache System Views.
Log in to the OMS Community Edition console.
In the left-side navigation pane, click Data Source Management.
On the Data Sources page, click More Actions > Cache System Views for the target OceanBase Database V3.x data source.
On the O&M Tasks page, wait for the O&M task to complete. The system views are cached when the task is complete.