1   说明

You can set the MAX_IOPS initialization parameter and the MAX_MBPS initialization parameter to limit the disk I/O generated by a PDB.

主要是为了限制PDB的I/O，来控制整体CDB性能，保证其他PDB能有足够的I/O资源可用。

A large amount of disk I/O can cause poor performance. Several factors can result in excess disk I/O, such as poorly designed SQL or index and table scans in high-volume transactions. If one PDB is generating a large amount of disk I/O, then it can degrade the performance of other PDBs in the same CDB.

①　 The MAX_IOPS initialization parameter limits the number of I/O operations for each second. --限制I/O次数http://www.cndba.cn/Expect-le/article/2075

②　 The MAX_MBPS initialization parameter limits the megabytes for I/O operations for each second. --限制I/O字节数

注意：如果在CDB级别设置这两个参数，那么会限制CDB里的所有PDB I/O

1.1   设置方式

SQL> ALTER SYSTEM SET MAX_IOPS = 1000 SCOPE = BOTH;

System altered.

SQL> ALTER SYSTEM SET MAX_MBPS = 5 SCOPE = BOTH;

System altered.

http://www.cndba.cn/Expect-le/article/2075

1.2   查看PDB I/O使用情况

You can use the DBA_HIST_RSRC_PDB_METRIC view to calculate a reasonable I/O limit for a PDB. Consider the values in the following columns when calculating a limit: IOPS, IOMBPS, IOPS_THROTTLE_EXEMPT, and IOMBPS_THROTTLE_EXEMPT. The "rsmgr:io rate limit" wait event indicates that a limit was reached.http://www.cndba.cn/Expect-le/article/2075

您可以使用DBA_HIST_RSRC_PDB_METRIC视图来计算PDB的合理I / O限制。 在计算限制时，请考虑以下列中的值：IOPS，IOMBPS，IOPS_THROTTLE_EXEMPT和IOMBPS_THROTTLE_EXEMPT。 “rsmgr：io rate limit”等待事件表示达到I/O限制。

更多信息，请查看官方文档：

http://docs.oracle.com/database/122/ADMIN/using-oracle-resource-manager-for-pdbs-with-sql-plus.htm#ADMIN13789http://www.cndba.cn/Expect-le/article/2075

 http://www.cndba.cn/Expect-le/article/2075

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IO Rate Limits for PDBs