6.6.3 MIF-to-MIB Mapping

The mapping of MIF to MIB involves the assignment of an OID from the MIF. A translator (miftomib.EXE) is available to build a file extension of .MAP and a .MIB file from a MIF definition. The translator may be used as a tool to generate the .MIB and the .MAP files. Or, the map file may be generated manually, using a text editor. All .MAP files located in the directory under /var/dmi/map are scanned and included in the subagent translation table.

Figure 6-2 MIF-to-MIB Mapping

The map file format is shown in Table 6-2.

Table 6-2 Map File Format

OID Prefix	Component Name
"1.3.6.1.4.1.42.2000.2"	"Client Access/400 Family - Base Product"

The design approach is to map the DMI component ID, group ID, and attribute ID to MIB object IDs. The managing entity must predetermine the MIB definition to be used by the mapper to map to the MIF definition. Using a miftomib translator to produce the MIB mapping file facilitates the mapping.

The map file is generated externally to the mapper. A mechanism is required to notify the mapper of new or updated files on the system in order to enable the new MIF definitions to be dynamically added. This is accomplished by using the DmiGroupAdded indication, delivered by dmispd, when the mapper rereads all the .MAP files.

See Figure 6-3 for examples of the OID prefix and the completed OID layout. The mapping file is used by the mapper to register the OID with the SNMP agent relay and to correlate the OID with the component name. It contains the component ID and the group keys, in case the group contains tabular data.

The mapper puts no restriction on what the OID prefix may be. That is controlled by the network administrator. Any OID may be entered into a .MAP file, provided the SNMP Master Agent allows the subtree registration. In the case of failure, the .MAP file needs to be changed for the OID correction.

Figure 6-3 MIB OID Layout

Parts of the object identifier are shown below:

• Object Identifier: OID-prefix: 1.3.6.1.4.1.42.2000.x

• OID for Groups: .1

• Object-type for Table: .iGroupID

• Object-type for Row: .1

• Attribute Identifier: .iAttributeId

• Instance Identifier: Indexes: .iComponentId <keys>

The example in Table 6-3 shows OIDs for client access attributes (no keys).

Table 6-3 OIDs for Client Access Attributes

Object Identifier:   OID-prefix	OID for Groups	Object-type for Table	Object-type for Row	Attribute Identifier: Object-type for Column	Instance Identifier: Indexes
1.3.6.1.4.1.42.2000.x	.1	.1	.1	.1	.3

Retrieving objects via the GetNext operation must be specially handled, since MIB tables are traversed column-by-column and MIF tables are traversed row-by-row.