Oracle 参数 AWR_SNAPSHOT_TIME_OFFSET 官方解释，作用，如何配置最优化建议
本站中文解释
AWR_SNAPSHOT_TIME_OFFSET 是Oracle 单个实例内置参数，表示收集AWR快照之间的时间间隔，默认值为 60 秒，最低设置为 30 秒 ，最大设置为 86400 秒（即一天）。
要正确设置AWR_SNAPSHOT_TIME_OFFSET 参数，可以参考如下步骤：
1.确定需要设置的初始值，建议根据应用要求，及实例的负载情况确定初始值；
2.登陆数据库，使用命令 ALTER SYSTEM RESET AWR_SNAPSHOT_TIME_OFFSET 进行重置修改，命令格式如下：
ALTER SYSTEM SET awr_snapshot_time_offset = ‘[值]’ SCOPE = SPFILE;
3.使用shutdown immediate或shutdown abort重启数据库，使参数修改生效；
4.使用 show parameter awr_snapshot_time_offset检查参数值是否正确性设置。
官方英文解释
AWR_SNAPSHOT_TIME_OFFSET specifies an offset for the Automatic Workload Repository (AWR) snapshot start time.
| Property | Description |
|---|---|
|
Parameter type |
Integer |
|
Default value |
There is no offset by default. |
|
Modifiable |
|
|
Modifiable in a PDB |
No |
|
Range of values |
0 – 3599, or the special value 1000000 |
|
Basic |
No |
|
Oracle RAC |
Multiple instances should use the same value |
AWR snapshots normally start at the top of the hour (12:00, 1:00, 2:00, and so on). This parameter allows DBAs to specify an offset for the AWR snapshot start time.
This is a useful parameter to avoid CPU spikes from multiple instances all starting their AWR snapshots at the same time. If you have a large system with many instances on it (like many Exadata installations), and you are experiencing such CPU spikes, this parameter can be very useful.
The parameter is specified in seconds. Normally, you set it to a value less than 3600. If you set the special value 1000000 (1,000,000), you get an automatic mode, in which the offset is based on the database name.
The automatic mode is an effective way of getting a reasonable distribution of offset times when you have a very large number of instances running on the same node.
