Filter
Top Products
The node error table must be defined as a RESIDENT program. This makes it easy
for the NEP to find it (using a CICS LOAD request), and ensures that any counters
are not reset by reloading. You can give the table any name you like. The default is
DFHNET.
The table consists of sets of error-recording areas. Each set is called a node error
block (NEB) and is used to count node errors relating to a single LU. You can
dedicate specific NEBs to specific LUs throughout a CICS run; and you can leave
other, reusable NEBs for general use. If you expect to accumulate error statistics
about 10 LUs concurrently, you need 10–12 NEBs.
Each NEB may contain multiple recording areas, one being used for each group of
errors you want to distinguish. The error groups correspond to those in the NEP.
That is, they are groups of error types requiring separate processing logic.
Each recording area is known as an error status block (ESB). You specify the space
reserved for each ESB, and it typically includes space to count the errors, or record
when the first of the present series occurred. Note that in any one NEB the
counting is for one LU only.
Finally, you can specify a threshold count and a time limit in the table. These are
constants that can be used by code in the NEP to test an ESB, to see if a given
type of error has occurred more than the threshold number of times in the stated
interval. The time limit also affects the interval between using a general NEB for
one LU and then reusing it for another.
A minimal NET would simply consist of a handful of NEBs, each with just one ESB,
grouping together all types of error that are of interest.
Note: If you write your own node error program, you must generate a NET, even if
it contains no entries because your error processors do not use it.
Coding the sample NEP
The sample NEP is coded using the macro DFHSNEP. The basic form is as follows:
DFHSNEP TYPE=INITIAL
Specific error handling code. For example:
DFHSNEP TYPE=DEF3270
DFHSNEP TYPE=FINAL
END DFHNEPNA
By default, this generates a module called DFHZNEP, which works with a node
error table called DFHNET. If you want to use another table, you could code
NETNAME=MYTABLE after TYPE=INITIAL. Details of the DFHSNEP macro are
given in “Generating the sample node error program” on page 469.
To understand the sample code, generate a standard NEP, as with
TYPE=DEF3270, shown in “DFHSNEP TYPE=DEF3270—including error processors
for 3270 LUs” on page 470, and look at the resulting assembler-language listing.
Here is a description of the code.
The INITIAL and FINAL macros generate the basic skeleton of the NEP. This
comprises some initialization code and some common routines. All the code is built
round the assumption that you have a node error table as previously described.
background to VTAM error handling
Chapter 9. Writing a node error program 453