# 性能视图快照系统表
设置enable_wdr_snapshot为on后，后台快照线程会创建并维护以"SNAP_+视图名称"方式命名的系统表，用于记录各性能视图的快照结果。需要有系统管理员权限才可以访问下列系统表。
- SNAP_[PGXC_OS_RUN_INFO](https://support.huaweicloud.com/devg-dws/dws_04_0812.html)
- SNAP_[PGXC_WAIT_EVENTS](https://support.huaweicloud.com/devg-dws/dws_04_0832.html)
- SNAP_[PGXC_INSTR_UNIQUE_SQL](https://support.huaweicloud.com/devg-dws/dws_04_0808.html)
- SNAP_[PGXC_STAT_BAD_BLOCK](https://support.huaweicloud.com/devg-dws/dws_04_0821.html)
- SNAP_[PGXC_STAT_BGWRITER](https://support.huaweicloud.com/devg-dws/dws_04_0822.html)
- SNAP_[PGXC_STAT_REPLICATION](https://support.huaweicloud.com/devg-dws/dws_04_0824.html)
- SNAP_[PGXC_REPLICATION_SLOTS](https://support.huaweicloud.com/devg-dws/dws_04_0817.html)
- SNAP_[PGXC_SETTINGS](https://support.huaweicloud.com/devg-dws/dws_04_0819.html)
- SNAP_[PGXC_INSTANCE_TIME](https://support.huaweicloud.com/devg-dws/dws_04_0807.html)
- SNAP_[GLOBAL_WORKLOAD_TRANSACTION](https://support.huaweicloud.com/devg-dws/dws_04_0687.html)
- SNAP_[PGXC_WORKLOAD_SQL_COUNT](https://support.huaweicloud.com/devg-dws/dws_04_0843.html)
- SNAP_[PGXC_STAT_DATABASE](https://support.huaweicloud.com/devg-dws/dws_04_0823.html)
- SNAP_[GLOBAL_STAT_DATABASE](https://support.huaweicloud.com/devg-dws/dws_04_0684.html)
- SNAP_[PGXC_REDO_STAT](https://support.huaweicloud.com/devg-dws/dws_04_0815.html)
- SNAP_[GLOBAL_REDO_STAT](https://support.huaweicloud.com/devg-dws/dws_04_0682.html)
- SNAP_[PGXC_REL_IOSTAT](https://support.huaweicloud.com/devg-dws/dws_04_0816.html)
- SNAP_[GLOBAL_REL_IOSTAT](https://support.huaweicloud.com/devg-dws/dws_04_0683.html)
- SNAP_[PGXC_TOTAL_MEMORY_DETAIL](https://support.huaweicloud.com/devg-dws/dws_04_0827.html)
- SNAP_[PGXC_NODE_STAT_RESET_TIME](https://support.huaweicloud.com/devg-dws/dws_04_0811.html)
- SNAP_[PGXC_SQL_COUNT](https://support.huaweicloud.com/devg-dws/dws_04_0825.html)
- SNAP_[GLOBAL_TABLE_STAT](https://support.huaweicloud.com/devg-dws/dws_04_0962.html)
- SNAP_[GLOBAL_TABLE_CHANGE_STAT](https://support.huaweicloud.com/devg-dws/dws_04_0963.html)
- SNAP_[GLOBAL_COLUMN_TABLE_IO_STAT](https://support.huaweicloud.com/devg-dws/dws_04_0964.html)
- SNAP_[GLOBAL_ROW_TABLE_IO_STAT](https://support.huaweicloud.com/devg-dws/dws_04_0965.html)
此类系统表除增加snapshot_id字段（bigint类型）外，其余的字段定义与对应视图相同，且各表的分布键均为snapshot_id。
例如，SNAP_PGXC_OS_RUN_INFO，用于存储PGXC_OS_RUN_INFO视图的快照，其字段新增了snapshot_id，其余字段含义均与PGXC_OS_RUN_INFO视图相同。
![](https://support.huaweicloud.com/devg-dws/public_sys-resources/notice_3.0-zh-cn.png)
- 以上系统表的schema都是dbms_om。
- 禁止从外部修改或删除以上系统表，否则可能引起视图快照相关功能异常。