http://blog.163.com/succu/blog/static/193917174201252911727149/
1.sessionsAmong the limits set by the initialization parameters, the best known estimate is that the Sessions and processes Sessions parameters specify the number of Sessions that can exist in a instance, or the number of concurrent users that can log in to the database at the same time. In general, we need to think about how many concurrent users we might have connected to the database at the same time, plus the number of processes in the background process, and finally multiply with 1.1. For example, it is estimated that the system may have 100 users connected to the database at the same time, then your session should be at least (100 + 10) * 1.1 = 121 When the concurrent user of the database connection has reached this value, and a new session is connected, it will error 00018, 00000 , "maximum number of sessions exceeded"//*cause:all Session state objects is in use.//*action:increase the value of T He SESSIONS initialization parameter.
2. Processes and sessions are similar to processes this parameter. The processes parameter specifies the number of processes that instance can run concurrently at the OS level. Based on the same considerations as sessions, when setting up processes, we should also consider how many concurrent users we might have connected to the database at the same time, plus the number of processes in the background process. Of course, in the configuration of MTS (Shared server), this value will be determined differently. The number of processes that should be normal background process + maximum shared server (max_shared_servers) + Maximum dispatcher processes (Max_dispatchers) . in addition, because in the window platform, Oracle is the,processes parameter in the form of a single process that has become a limit on the number of threads in the Oracle process. When Oracle needs to start a new process and has reached the processes parameter, it will get an error: 00020, 00000, "Maximum number of processes (%s) Exceeded "//*cause:all process state objects is in use.//*action:increase the value of the processes initial ization parameter. 1). Modifying Oracle's sessions and processes relationships through Sqlplus is sessions=1.1*processes + 5 using SYS, Login with SYSDBA permissions: sql> show Parameter processes;name TYPE VALUE------------------------------------------- -------------------------------------------Aq_tm_processes integer 1db_writer_processes integer 1job_ Queue_processes integer 10log_archive_max_processes integer 1proCesses integer 150 sql> alter system set processes=400 scope = SPFile; SQL> show Parameter processes;name TYPE VALUE------------------------------------------------------- ---------------------------------Aq_tm_processes integer 1db_writer_processes integer 1job_queue_ Processes integer 10log_archive_max_processes integer 1processes integer 150 SQL> Create Pfile from SPFile; The file has been created. Restart database, ok! SQL> shutdown immediate; The database is closed. The database has been uninstalled. The oracle routine has been closed. The SQL> startuporacle routine has been started. total System Global area 171966464 bytesfixed size 787988 bytesvariable size 145488364 bytesdatabase buffers 25165824 Bytesredo buffers 524288 bytes Database is loaded. The database is already open. SQL> Show parameter processes; name type VALUE---------------------------------------------------------------aq_tm_processes integer 0db_writer_processes integer 1gcs_server_processes integer 0job_queue_processes integer 10log_archive_max_ processes integer 2processes integer 400 sql > Show Parameter session; name type VALUE----------------------------------------------- ----------------java_max_sessionspace_size Integer 0java_soft_sessionspace_limit Integer   0license_max_sessions integer 0license_sessions_warning integer 0logmnr_max_persistent_sessions integer 1session_cached_cursors integer 0session_max_open_files integer 10sessions integer 445shared_server_sessions Integersql> "Note: Sessions is a derived value, determined by the value of processes, the formula Sessions=1.1*process + 5"
Initial settings for session and processes in Oracle
