I/O Rate Limits for PDBs 12.2 New feature .
(Doc ID 2164827.1)
Last updated on JANUARY 09, 2020
Applies to:Oracle Database - Enterprise Edition - Version 220.127.116.11 and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Information in this document applies to any platform.
This feature limits the rate of physical I/O issued by a pluggable database (PDB). You can specify the limit as either I/O requests per second or as Mbps (megabytes of I/O per second). This limit can only be applied to a PDB, not to the multitenant container database (CDB) or a non-CDB.
Background I/O, such as redo log writes or dirty buffer cache writes, are not limited. The limits are specified with the new PDB parameters, MAX_IOPS and MAX_MBPS.
You can set the MAX_IOPS initialization parameter and the MAX_MBPS initialization parameter to limit the disk I/O generated by a PDB.
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.
Use one or both of the following initialization parameters to limit the I/O generated by a particular PDB:
The MAX_IOPS initialization parameter limits the number of I/O operations for each second.
The MAX_MBPS initialization parameter limits the megabytes for I/O operations for each second.
Both limits are enforced if you set both initialization parameters for a single PDB.
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