Oracle Parameter Processes and Sessions

[srinivasan_vinayagam]

^{The Oracle Parameter}

^Processes

PROCESSES DEFINITION

Parameter type	Integer
Default value	Derived from PARALLEL_MAX_SERVERS
Parameter class	Static
Range of values	6 to operating system-dependent
Real Application Clusters	Multiple instances can have different values.

PROCESSES specifies the maximum number of operating system user processes that can simultaneously connect to Oracle. Its value should allow for all background processes such as locks, job queue processes, and parallel execution processes.

The default values of the SESSIONS and TRANSACTIONS parameters are derived from this parameter. Therefore, if you change the value of PROCESSES, you should evaluate whether to adjust the values of those derived parameters.

http://docs.oracle.com/cd/B10501_01/server.920/a96536/ch1168.htm#REFRN10175

Specifying the Maximum Number of Processes

The PROCESSES initialization parameter determines the maximum number of operating system processes that can be connected to Oracle Database concurrently. The value of this parameter must be a minimum of one for each background process plus one for each user process. The number of background processes will vary according the database features that you are using. For example, if you are using Advanced Queuing or the file mapping feature, you will have additional background processes. If you are using Automatic Storage Management, then add three additional processes for the database instance.

If you plan on running 50 user processes, a good estimate would be to set the PROCESSES initialization parameter to 70.

http://docs.oracle.com/cd/B28359_01/server.111/b28310/create005.htm#ADMIN11108

SAP Notes:

221643 - Oracle Message: "ERROR system.database - ORA-00020: maximum number of     processes (%s) ex... 

34432 - ORA-00020: maximum number of processes exceeded

SAP Notes for Recommended Oracle Parameters:

830576 - Parameter recommendations for Oracle 10g

1431798 - Oracle 11.2.0: Database Parameter Settings

Error Captured:

Backup Failed: http://scn.sap.com/thread/1398677

Archival failed with below reason http://scn.sap.com/thread/1251972

Solution Manager crashes every two week or so: http://scn.sap.com/thread/3333727

Background jobs failed http://scn.sap.com/thread/1980217

Database check failed: http://scn.sap.com/thread/1226748

Transport Terminated: http://scn.sap.com/thread/461606

Error in Portal System: http://scn.sap.com/thread/18638

Check Current Value of Processes:

ST04 / DBCOCKPIT Transaction

SPFILE Entry in ST04

Current Used Processes Value

Compare the PIDs on task manager

Calculation of Processes by Hardware of System:

Parallel_max_servers calculation

PARALLEL_MAX_SERVERS depends on the CPU cores in the database server available for database (total CPU cores on database server minus CPU requirements of other applications including SAP central instance)

PARALLEL_MAX_SERVERS = Number of DB machine CPU CORES*10

For example for ABAP Stack:

Number of CPU = 4

Parallel_Max_Servers = 4 * 10 = 40

ABAP Work Processes = 25

Processes = (ABAP Work Processes * 2) + Parallel_Max_Servers + 40 = (25*2) + 40 + 40 = 130

Session = 2 * Processes = 260

For example for JAVA Stack

PROCESSES = J2EE server processes * <max-connections> + PARALLEL_MAX_SERVERS + 40

J2EE Server Processes = 2 (if two server nodes – Server0 and Server1)

Max Connections = Open the Visual Administrator and select Server <X> -> Services -> JDBC Connector = 50

PROCESSES = 2*50 + 40 + 40 = 180

Session = 180 * 2 = 360

SESSIONS CALCULATION:

SESSIONS

2 * PROCESSES