Code:

PROCNAME=`basename $0 | awk -F"." '{print $1}'`

Fills the variable PROCNAME with the basename (without path if existed), uses a dot as field seperator, and used the first part of the filename which was limited by dot/s.

Code:

export LOG_DT=`date '+20%y%m%d'`;

Fills and exports the variabe LOG_DT with the value of date, though should have used %Y rather than 20%y

Code:

export LOG_TM=`date +'%H%M'`.log;

Similar as above but with time, and appending the .log extension to the string.

Code:

export FCTN_LIB=${ARCH_BIN_DIR}/function_library.sh

Fills and exports the variable FCTN_LIB with the (undefiend) variable ARCH_BIN_DIR, and appending the filename function_library.sh.

Code:

. ${FCTN_LIB}

Sourcing the above defined file.

Code:

export LOG=${LOG_DIR}/${PROCNAME}.${LOG_DT}${LOG_TM}

Finaly the LOG variable gets filled and exported by appending the above strings together.

Code:

export PFILE=${PROCNAME}.ksh_param

Yet another PFILE variable, which is named the same as the script beeing executed, but having .ksh_param extension, rather than what was originaly.

Code:

PGM=${PROCNAME}

Fill another variable with the basename without file extension to PGM.

Code:

clear

Clear the screen, not that anything was printed yet...

Code:

trap 'errhandle_se_je 1' 1 2 3 15

Trying to trap a function, which was not defined in the given code, while passing 1 2 3 15.
There seems an error, as the first 1 is inside the quote to the function, which probably will cause the function to fail, since its quote, and since there is a space inside the quotes.

Code:

A=${1:-0}
B=${2:-0}  
C=${3:-0}

Filling variable A,B,C with the values of passed arguments 1,2,3 while cut off the 0 tailing chars.

Code:

D=${4:-30}
E=${5:-270}

Same as above, but cutting off 30 (D) or 270 (E) tailing chars (from the right!)

Code:

F="$CDD/${PROCNAME}_dups.bad

Fills the variable F with undefiend variable CDD as path and using PROCNAME (not PGM with the same content) and yet another file extension: .bad.

Hope this helps to get you started