This topic describes the background information and procedure for caching system views.
Background information
In OceanBase Database V3.x, major views related to statistics, tables, and columns in the information_schema database have no indexes. When you migrate a large amount of data from many tables in OceanBase Database V3.x to OceanBase Database V4.x, you will fail to create a data migration task because each query is a full-table scan, full-table scans are frequently performed in schema migration and full migration, and many queries must be executed on each table.
To address this issue, OceanBase Migration Service (OMS) Community Edition V4.2.5 allows you to cache the system metadata views used in OceanBase Database V3.x to the local storage. You can create a data migration task after the system views are cached. OMS Community Edition automatically uses the cached data. The cached files are stored in the root directory /home/ds/run/sysmetacache/{endpointId}.
Limitations
At present, OMS Community Edition allows you to cache system views only for OceanBase Database V3.x.
Procedure
To cache system views, perform the following steps:
Log in to the console of OMS Community Edition.
In the left-side navigation pane, click Data Source Management.
On the Data Sources page, click the More icon in the Actions column of the data source and then select Cache System View from the drop-down list.
The O&M task page appears. Wait until the O&M task is completed.