Defining an IAM Path

Defining a Path

The process of defining a PATH to an IAM Alternate Index or base cluster is essentially the same as with VSAM. IAM will automatically determine if the PATHENTRY is an IAM data set, so use of the OWNER($IAM) parameter is optional. AnIAM path is a one-track data set. The allocation request will be made for the same volume on which the path entry data set resides. If the path entry data set is DFSMS managed, the path data set will be allocated with the same SMS classes as the path entry data set. IAM uses the one track data set to store information about the relationship of the path to its Alternate Index or base cluster, rather than using a catalog entry. The IAM path data set does not have to be on the same volume with the related data set, although IAM attempts to place it there.

IDCAMS Define Path

IDCAMS can be used to define a path. On the DEFINE PATH command, the PATHENTRY keyword indicates the related data set. To access a base cluster through an Alternate Index, the PATHENTRY will be the name of the Alternate Index. The attribute UPDATE (or NOUPDATE) indicates whether the upgrade set of the Alternate Indexes will also be opened. The upgrade set includes all Alternate Indexes defined with the UPGRADE attribute.

If only the base cluster is being opened for update, any upgradeable Alternate Index data sets will also be opened. To prevent Alternate Index upgrades, define a PATH for the base cluster with the NOUPDATE attribute.

An example of defining an IAM PATH with IDCAMS is shown below.

Example of Using IDCAMS to Define a Path (EX1063A)

//DEFPATH EXEC PGM=IDCAMS
//SYSPRINT DD   SYSOUT=*
//SYSIN    DD   *
  DEFINE PATH -
    (NAME(example.iam.path) -
    PATHENTRY(example.iam.aix) -
    UPDATE )
/*

IAM ISPF Define Path

If you have the IAM ISPF panels installed, they also provide a Define Path function. Starting at the IAM Primary Options menu, as shown below, select option I to define an IAM data set then enter the name of the path that you want to define, and indicate a P for data set type, indicating a path. An example of the completed panel is shown below.

IAM ISPF Define of a Path

After pressing ENTER, IAM will display the IAM Define Path panel as shown below. On this panel, enter the fully qualified name of the path entry data set, which is either an Alternate Index or a base cluster. Also enter whether or not the upgrade set is to be opened if the path is opened for update. While a specification of NO will eliminate the overhead of updating all of the Alternate Indexes in the upgrade set, the Alternate Indexes will not properly reflect the contents of the base cluster.

IAM ISPF Define an IAM Path Panel

After pressing ENTER, IAM will return to the IAM Primary Options panel, with a message in the upper right hand corner indicating that the path was successfully allocated. To display the attributes of the Path, press ENTER again, with the Path name in the data set name field.

IAM Path Display

The IAM Path Characteristics panel displays basic information about the actual data record that would be retrieved from the base cluster through this path. Because the IAM Path data set is an actual one track data set, volser and device type information is displayed. At the bottom are the associations indicating the data sets related to this path.

IAM Path Characteristics Panel