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Introduction to the BEA WebLogic Server SNMP MIB

This section discusses the following topics:

- MIB Object Identifiers

- Structure of the MIB Definitions

The WebLogic Administration Server has the ability to function as a Simple Network Management Protocol (SNMP) agent. The WebLogic SNMP agent runs as a service which responds to requests from SNMP managers and sends SNMP trap notifications to SNMP managers. The WebLogic SNMP agent uses standard Java Management Extension (JMX) interfaces to access WebLogic attributes. The agent provides the following capabilities:

- Access (GET) runtime information to monitor attributes available via JMX Management Beans (MBeans) on the Administration Server

- Access (GET) WebLogic domain configuration information via JMX MBeans on the Administration Server

- Subscribe for JMX notifications generated by WebLogic Servers, for monitoring or logging events

- Support for configurable log-based enterprise-specific SNMP trap notifications

- Introduce a user-defined SNMP Management Information Base (MIB), to extend manageability of a WebLogic implementation, without modifying the WebLogic SNMP agent

There are two types of MBeans that reside on the Administration Server. Runtime MBeans can obtain (GET) monitoring information about the current state of WebLogic resources (see BEA WebLogic Server Runtime MIB). Configuration MBeans (see BEA WebLogic Server Configuration MIB) enable the Administration Server to both modify (SET) configuration attributes of resources as well as obtaining (GET) information about the current state of configurable attributes. In this release of the SNMP service for WebLogic Server, only the retrieval (GET) of configuration attribute information is supported.

MIB Object Identifiers

In the SNMP management framework, a resource is said to be manageable if SNMP requests can obtain (GET) information about the values of its attributes or modify (SET) the values of such attributes. In the world of the SNMP management software, manageable attributes are called objects and are arranged in a hierarchy of information known as a Management Information Base (MIB). Each object in the MIB has an object identifier (OID), which the manager uses to request the object's value from the agent. An OID is a sequence of integers that uniquely identifies a managed object by defining a path to that object through a tree-like structure called the OID tree or registration tree. When an SNMP agent needs to access a specific managed object, it traverses the OID tree to find the object.

Figure 1-1 The WebLogic Object Identifier

For WebLogic Server, the manageable attributes are defined as SNMP objects in the BEA Weblogic private MIB file included with the WebLogic Server software. This file is named BEA-WEBLOGIC-MIB.asn1.

In this hierarchy, each BEA WebLogic private MIB object that the WebLogic agent software manages has a unique object identifier. The BEA WebLogic object uses a prefix of .1.3.6.1.4.1.140.625 to identify it as an object in the BEA private MIB. For a complete listing of objects in the BEA WebLogic private MIB in ASN.1 notation, read the BEA WebLogic ASN.1 file.

ASN.1 File

The BEA WebLogic SNMP MIB conforms to a coding standard called Abstract Syntax Notation.1 (ASN.1). An ASN.1 file is a standard SNMP file that defines the objects that make up an SNMP-compliant MIB. Each object in the file is defined in compliance with the SNMP standard. The BEA WebLogic Server software includes the the ASN.1 file BEA-WEBLOGIC-MIB.asn1 for defining the BEA WebLogic MIB for SNMP. The BEA WebLogic SNMP MIB is written in compliance with RFC 1212, as required by the SNMP standard.

Relative and Absolute Object Identifiers

OIDs can be specified in two ways: relative and absolute. Absolute OIDs specify a path to an attribute from the root of the OID tree. Absolute OID names always begin with a dot and must specify every node of the OID tree from the top-most node to the specific managed object. For example:

>     .1.3.6.1.2.1.1.1

Relative OIDs specify a path to the attribute relative to some node in the OID tree. For example,

>     2.1.1.7

specifies the MIBII sysContact object in the system group, relative to the Internet node in the OID tree.

Specifying Object Identifiers

In addition to using the "dot-dot" notation — a series of integers separated by dots to describe OIDs — you can also express OIDs by using textual symbols instead of numbers to represent nodes in the path to the object, or by using a combination of both integers and textual symbols. A symbolic OID uses mnemonic keywords to specify the managed object. For example:

>     mgmt.mib-2.system.sysDescr

The following numeric OID uses integers to specify the same managed object:

>     2.1.1.1

Note that this example is a relative OID.

An OID can combine both symbolic and numeric representations of individual nodes of the OID tree; for example:

>     mgmt.mib-2.1.sysDescr

You can find mnemonic or textual equivalents of OID nodes in the WebLogic private MIB by consulting the WebLogic ASN.1 file. The textual equivalent for 625, the WebLogic Server node in the registration tree (.1.3.6.1.4.1.140.625), is wls.

Structure of the MIB Definitions

The following keywords are used to define MIB managed objects:

  Syntax

  Defines the abstract data structure corresponding to that object type. The ASN.1 language is used for this purpose. However, the SMI purposely restricts the ASN.1 constructs that can be used. These restrictions are made expressly for simplicity.

  Access

  Defines whether the object value can only be retrieved but not modified (read-only) or whether it can also be modified (read-write).

Note: For tabular objects, in some cases a read-write object can only be set during creation of a new row. Where this is true, it is noted in the Description section for that MIB object.

  Description

  Contains a textual definition of that object type that provides all semantic definitions necessary for interpretation. This clause typically contains information of the sort that would be communicated in any ASN.1 commentary annotations associated with the object.

Note: Each row in a table is an instance of the Entry object under that table. The Description section for the Entry object under a table (such as jdbcConnectionPoolTable) contains information on the columnar values that are minimally necessary for creation of a row-how a new row is created, whether the values pertain only to the local machine, and other pertinent information about the table objects.

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