1 Oracle Database Architecture on Windows

Oracle Automatic Storage Management

Oracle Automatic Storage Management (Oracle ASM) is an integrated file system and volume manager expressly built for Oracle Database files. Oracle ASM provides the performance of raw I/O with the easy management of a file system. It simplifies database administration by eliminating the need for you to directly manage potentially thousands of Oracle Database files. It enables you to divide all available storage into disk groups. You manage a small set of disk groups, and Oracle ASM automates the placement of the database files within those disk groups.

Oracle recommends that you use Oracle ASM instead of raw files to store data files. It provides the performance benefits of raw files with much better manageability. Oracle ASM is available for both single instance and Oracle Real Application Clusters (Oracle RAC) databases.

You can store Oracle Cluster Registry and voting files in Oracle ASM disk groups and store database data files in the data disk group. The voting files and Oracle Cluster Registry are two important components of Oracle Clusterware.

Oracle Automatic Storage Management File Access Control

Oracle ASM File Access Control restricts the access of files to specific Oracle ASM clients that connect as SYSDBA. An Oracle ASM client is a database, which is identified by the name of the user that owns the database instance home. Oracle ASM File Access Control uses this user name to identify a database. Oracle ASM File Access Control restricts access based on the operating system and effective user identification number of a database owner.

Thread-Based Architecture

The internal process architecture of Oracle Database is thread-based. Threads are objects within a process that run program instructions. Threads allow concurrent operations within a process so that a process can run different parts of its program simultaneously on different processors. A thread-based architecture provides the following advantages:

• Faster context switching

• Simpler System Global Area allocation routine, because it does not require use of shared memory

• Faster spawning of new connections, because threads are created more quickly than processes

• Decreased memory usage, because threads share more data structures than processes

Internally, the code to implement the thread model is compact and separate from the main body of Oracle Database code. Exception handlers and routines track and deallocate resources. They add robustness, with no downtime because of resource leaks or program that does not function as expected.

Oracle Database is not a typical Windows process. On Windows, an Oracle Database or Oracle Automatic Storage Management instance (threads and memory structures) is a Windows service: a background process registered with the operating system. The service is started by Windows and requires no user interaction to start. This enables the database to open automatically at computer startup.

When running multiple Oracle Database or Oracle Automatic Storage Management instances on Windows, each instance runs its own Windows service with multiple component threads. Each thread might be required for the database to be available, or it might be optional and specific to certain platforms. The background processes read and write from various data files, depending on your configuration. Oracle Database architecture on Windows is illustrated in Figure 1-1. Examples of Oracle Database required threads on Windows are listed in Table 1-1.

Figure 1-1 Oracle Database Architecture on Windows

Description of "Figure 1-1 Oracle Database Architecture on Windows"

SQL> select * from v$bgprocess where paddr <> '00'; 

Oracle Database for Windows is supplied as a set of executables and dynamic link libraries (DLLs). Executable images can be modified using ORASTACK to change the size of the stack used by the threads of the Oracle Database process. Oracle recommends that you use this tool only under the guidance of Oracle Support Services.

File I/O Enhancements

Oracle Database supports 64-bit file I/O to allow use of files larger than 4 gigabytes (GB). In addition, physical and logical raw files are supported as data, log, and control files to support Oracle Real Application Clusters (Oracle RAC) on Windows and for those cases where performance must be maximized.

Starting with Oracle Database 11g, instead of using the operating system kernel NFS client, you can configure Oracle Database to access NFS V3 servers directly using an Oracle internal Direct NFS client. Through this integration, Oracle can optimize the I/O path between Oracle and the NFS server, resulting in significantly superior performance. In addition, Direct NFS client simplifies and optimizes the NFS client configuration for database workloads.

Volumes mounted through CIFS cannot be used for storing Oracle database files without configuring the Direct NFS client. The atomic write requirements needed for database writes are not guaranteed through the CIFS protocol. Consequently, CIFS can be used only for operating system-level commands such as, copy, move, and so on.

The Direct NFS client currently supports up to four parallel network paths to provide scalability and high availability. The Direct NFS client delivers optimized performance by automatically load balancing requests across all specified paths. If one network path fails, then the Direct NFS client resends commands over any remaining paths ensuring fault tolerance and high availability.

A new parameter called dnfs_batch_size has been added starting with Oracle Database 12c Release 1 (12.1) to control the number of asynchronous I/O operations that can be queued by an Oracle process when the Direct NFS client is enabled. Set this parameter only if the Direct NFS client is overwhelming the NFS server or the network. This parameter helps the user to manage the load that the Direct NFS client can generate. In typical environments, you must not set this parameter. The default value of this parameter is 4096. To reduce the Direct NFS client load, Oracle recommends a value of 128 that can be changed based on the NFS server performance.

Large User Populations

Several features allow Oracle Database to support an increasingly large number of database connections on Windows:

• The Shared Server Process, limits the number of threads needed in the Oracle Database process and supports over 10,000 simultaneous connections to a single database instance.

• Oracle Net multiplexing and connection pooling features allow a large configuration to connect more users to a single database instance.

• Oracle RAC raises connection counts dramatically by allowing multiple server computers to access the same database files, increasing the number of user connections by tens of thousands while increasing throughput.

  Note:

  Oracle RAC is only supported on 64-bit Windows server operating systems.

Oracle PKI Integration with Windows

Oracle Advanced Security includes Oracle PKI (public key infrastructure) integration for authentication and single sign-on. You can integrate Oracle-based applications with the PKI authentication and encryption framework, using Oracle Wallet Manager.

Oracle Services for Microsoft Transaction Server

Microsoft Transaction Server (MTS) is used in the middle tier as an application server for COM objects and transactions in distributed environments. Oracle Services for Microsoft Transaction Server allows Oracle Database to be used as a resource manager in Microsoft Transaction Server-coordinated transactions, providing strong integration between Oracle solutions and Microsoft Transaction Server. Oracle Services for Microsoft Transaction Server can operate with Oracle Database running on any operating system.

Oracle Database takes advantage of a native implementation and also stores recovery information in Oracle Database itself. Oracle Services for Microsoft Transaction Server allows development in all industry wide data access interfaces, including Oracle Call Interface (OCI), ActiveX Data Objects (ADO), OLE DB, and Open Database Connectivity (ODBC). The Oracle APIs, Oracle Data Provider for .NET and OCI, offer greatest efficiency.

Oracle Fail Safe Integration with Windows

Oracle Fail Safe ensures that Oracle Database (and also other Oracle and third-party applications) can be configured and managed for high availability on Windows clusters. An instance runs on only one node at a time.

A cluster is a group of independent computing systems that operates as a single virtual system, eliminating individual host systems as points of failure. Oracle Fail Safe works with Microsoft Windows Failover Clusters to ensure that if a failure occurs on one cluster system, then workloads running on that system fail over quickly and automatically to a surviving system. Oracle Database combined with Oracle Fail Safe on a Windows cluster ensures protection from both hardware and software failures.

For well-configured solutions, Oracle Fail Safe ensures a surviving system to be operational in less than a minute, even for heavily used databases.