Changes in Oracle Database 12c Release 2 (12.2.0.1)
The following are changes in Oracle Database Performance Tuning Guide for Oracle Database 12c Release 2 (12.2.0.1).
New Features
The following features are new in this release:
1.Per-process PGA limits
A runaway query consuming excessive amount of PGA memory can create a serious performance problem in Oracle Database. In a multitenant container database (CDB), this type of query can affect the performance of all the pluggable databases (PDBs). To prevent this issue, you can now specify an absolute limit for the amount of PGA memory that can be used by each session in a particular consumer group.
消耗过多PGA内存的失控查询可能会在Oracle数据库中造成严重的性能问题。 在多租户容器数据库(CDB)中，此类查询会影响所有可插拔数据库(PDB)的性能。 为了防止这个问题，您现在可以指定一个绝对限制，用于特定用户组中每个会话可以使用的PGA内存量。
2.Prespawned server processes
Oracle Database now prespawns pools of server processes when dedicated broker connection mode is enabled or threaded execution mode is enabled. This feature improves the client connection performance in these modes of database operation.
当启用专用代理程序连接模式或启用线程执行模式时，Oracle数据库现在预先分配服务器进程池。 此功能可提高这些数据库操作模式下的客户端连接性能。
3.Automatic Workload Repository (AWR) support for multitenant environment
You can now capture Automatic Workload Repository (AWR) data for the PDBs in a multitenant environment. This feature enables performance tuning of PDBs in a multitenant environment.
您现在可以在多租户环境中捕获PDB的自动工作量存储库(AWR)数据。 此功能可以在多租户环境中调整PDB的性能。
4.Automatic Workload Repository (AWR) support for Oracle Active Data Guard standby databases
You can now capture Automatic Workload Repository (AWR) data for Oracle Active Data Guard standby databases. This feature enables performance tuning of Oracle Active Data Guard standby databases.
您现在可以捕获Oracle Active Data Guard备用数据库的自动工作量存储库(AWR)数据。 此功能支持Oracle Active Data Guard备用数据库的性能调整。
5.Direct NFS Client performance improvement features – Parallel NFS and Direct NFS Dispatcher
Parallel NFS is an optional feature of Oracle Direct NFS Client that is introduced in NFS version 4.1. This feature enables highly scalable distributed NAS storage for better I/O performance.
The Direct NFS dispatcher feature consolidates the number of TCP connections that are created from a database instance to an NFS server. In large database deployments, using Direct NFS dispatcher improves scalability and network performance.
并行NFS是NFS版本4.1中引入的Oracle Direct NFS Client的可选功能。 此功能支持高度可扩展的分布式NAS存储，以提高I/O性能。
Direct NFS调度程序功能将从数据库实例创建的TCP连接数合并到NFS服务器。 在大型数据库部署中，使用Direct NFS调度器可以提高可伸缩性和网络性能。
6.Service-oriented buffer cache access optimization
Cluster-managed services allocate workloads across various Oracle Real Application Clusters (Oracle RAC) database instances. These services also access data from the Oracle RAC database instances and provide it to the applications requesting the data. The Service-oriented Buffer Cache Access Optimization feature allows Oracle RAC to cache service-specific data that is frequently accessed by each of these services, thus improving the data access time for the services. This data-dependent caching also leads to more consistent response times when accessing data across Oracle RAC database instances. This feature is permanently enabled in Oracle RAC.
集群管理的服务在各个Oracle Real Application Clusters(Oracle RAC)数据库实例中分配工作负载。 这些服务还从Oracle RAC数据库实例访问数据，并将其提供给请求数据的应用程序。 面向服务的缓冲区缓存访问优化功能允许Oracle RAC缓存每个服务经常访问的特定于服务的数据，从而缩短服务的数据访问时间。 在跨Oracle RAC数据库实例访问数据时，这种依赖于数据的高速缓存也会导致更一致的响应时间。 此功能在Oracle RAC中永久启用。