Solution Guide for Migrating Oracle on UNIX to SQL Server - Willy .Net

338 AppendicesProcess/Thread ArchitectureThe process architecture identifies the various database related processes and theirfunctionality. As is true with <strong>Oracle</strong> on Windows, SQL Server also uses a thread-basedarchitecture. SQL Server does not differ significantly from <strong>Oracle</strong> in its use of pools ofprocesses (threads) <strong>for</strong> system functions and user requests. Table A.1 compares SQLServer functionality with respect to <strong>Oracle</strong> background processes.Table A.1: Mapping of <strong>Oracle</strong> and SQL Server Background Processes<strong>Oracle</strong> Process(Required Status)*<strong>Oracle</strong>IdentifierMin / MaxSQL Server Process(Required Status)*Min / MaxProcess Monitor (M) PMON 1 / 1 Open Data Services (M) 1 / 1System Monitor (M) SMON 1 / 1 Database cleanup / 1 / 1shrinking (M)Database Writers (M) DBWn 1 / 20 Lazywriter (M) 1 / 1Checkpoint Process (M) CKPT 1 / 1 Database checkpoint (M) 1 / 1Recoverer (O) RECO 0 / 1 MS DTC (O) 0 / 1Log Writer (M) LGWR 1 / 1 Logwriter (M) 1 / 1Archive Processes (O) ARCn 0 / 10 N/AJob Queue Processes Jnnn 0 / 1000 SQL Agent (O) 0 / 1(O)Job Queue Coordinators CJQn 0 / 1 SQL Agent (O)0 / 1(O)Queue MonitorQMNn 0 / 10 SQL Agent (O) 0 / 1Processes (O)Parallel Query Slave Pnnn 0 / 3600 Worker threads (M) 32 / 32767Processes (O)Dispatcher (O) Dnnn 0 / 5 Network thread (M) 1 / 1Shared Servers (O) Snnn 0 / OS Worker threads (M) 32 / 32767SQL Server employs sophisticated shared server architecture. On startup, SQL Servercreates a User Mode Scheduler (UMS) o bject <strong>for</strong> each processor using the affinity masksetting. A pool of worker threads is created by Open Data Services (ODS) to handle usercommands, and their control is distributed among the UMS schedulers. This architecturemimics the shared server-dispatcher concept in <strong>Oracle</strong>. While in <strong>Oracle</strong> the shared serverprocesses are schedule d by the operating system, SQL Server uses the UMS toschedule worker threads.The internal workings of the User Mode Scheduler are available at:http://msdn.microsoft.com/SQL/sqlarchitectu re /default.aspx?pull=/library/en-us/dnsqldev/html/sqldev_02252004.asp?frame=true.Additional references on topics related to process architecture include:● Server Memory Options (Administrating SQL Server):http://msdn.microsoft.com/library/default.asp?url=/library/en-us/adminsql/ad_config_9zfy.asp.● SQL Server Memory Usage: http://support.microsoft.com/default.aspx?scid=kb;enus;321363.● 64-bit Overview: http://www.microsoft.com/sql/64bit/productinfo/overview.asp.