Friday, May 29, 2009

Dynamic System Configuration

Use

The main idea of dynamic system configuration is to use parameterized settings instead of static values for system-dependent configuration. Thus, if the system environment is changed or new hardware is added, the overall configuration is changed dynamically without the need to adapt the configuration in the database manually.

Features

Parameterized Settings

Parameterized settings contain parameters specified in the instance profile provided within the Configuration Manager. These parameters are transparently substituted during runtime.

The structure of a parameter is ${}.

For example: Message Server host: ${MSGSRV_HOST}

Computed Settings

Computed settings are used in case a simple parameter substitution is not sufficient and the value needs to be calculated out of specific system parameters (such as heap size, cache size).

Computed settings are arithmetic expressions containing system parameters from the instance profile. The parameters are transparently substituted and the arithmetic expression is evaluated during runtime.

An arithmetic expression consists of parameters, constants, simple operators and brackets. Operators supported are “+”, ”-“, ”*”,” /”; “min”, “max” , “round” and “truncate” function;

Format: expr = expr1 min expr2 [corresponds to expr = min(expr1, expr2)].

round(${AMOUNT_MEMORY}/3)

For example: Number of Server Nodes per Instance: 2*${CPU_COUNT}

Value Links

Value links contain links to other settings in case a setting is dependent on another setting stored somewhere else in the Configuration Manager. A value link is transparently resolved and substituted during runtime.

The structure of a value link is $link{#}

Caution

Value links are intended for internal use only.

Instance Profile

The Zero Administration instance profile is a defined set of system-dependent configuration parameters provided by the Configuration Manager. They include:

SAP system parameters

Java instance parameters

Hardware and OS parameters

Node-specific parameters

The instance profile parameters can be referenced by using parameterized settings.

Instance Profile

The following table lists the current instance profile parameter set provided by the Configuration Manager.

Parameter

Description

SAP system parameters

${SYSTEM_NAME}

The three-character name of the system (for example, D70).

${SYS_GLOBAL_DIR}

The path to the system global share (for example, \\centralhost\sapmnt\D70\SYS\global).

${SYS_DATASOURCE_NAME}

The name of the system data source (for example, SAPN69DB).

${MSGSRV_HOST}

Host where the Message Server is located.

${MSGSRV_PORT}

Port of the Message Server.

${ENQSRV_HOST}

Host where the Enqueue Server is located.

${ENQSRV_PORT}

Port of the Enqeue Server.

${START_TIME}

Start time of the instance as a long value.

Java instance parameters

${INSTANCE_ID}

The ID of the current instance.

${INSTANCE_NAME}

The name of the current instance (for example, 'JC20' or 'J20' for a dialog instance).

${INSTANCE_NUMBER}

The number of the current instance (for example, for instance 'JC20' the number is '20').

${INSTANCE_HOST}

The host name of the host on which the instance is running.

${INSTANCE_DIR}

Path to the instance folder (for example, c:\usr\sap\D70\JC20).

${FULL_INSTANCE_NAME}

The full instance name of the current instance (for example, D70_JC20_pcj2ee01, where D70 is system name; JC20 is instance name and pcj2ee01 is instance host).

${SYSTEM_INFO}

The configuration path to the System Info configuration, which exposes parameters for the usage in the components configuration.

${JAVA_HOME}

The path to the bin folder of the Java installation.

${DB_DRIVER_LOCATION}

The driver location string specifying the driver location needed for the DB connection.

${VM_VENDOR}

The name of the VM vendor (for example, SAP).

${EXE_DIR}

Directory where native executables are located.

Hardware and OS parameters

${CPU_COUNT}

The number of CPUs available on the host which should be used by the instance.

${AMOUNT_MEMORY}

The amount of physical memory on the host which should be used by the instance.

${OS_NAME}

The SAP name of the OS.

${OS_BITLENGTH}

The bit length (for example, 32, 64) of the platform.

${OS_UNICODE}

Specifies if platform is Unicode enabled or not (uc, nuc).

Node-specific parameters

${NODE_INDEX}

Instance unique ID identifying a cluster node on an instance.

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