IBM Mainframe Forum

Hi,
I am new to assembler. I have been reading assembler for past few days and practicing. Everything was going fine untill i started with ISAM files.I have written an assembler program to read a ps file and store the data in the ISAM file. This program went fine. I have even checked the data using the idcams and everything seems to be fine.
Next i wrote a program to read the isam and store it back in ps file. But this time my program failed with the abend code S03b . when checked in net, i found the following reasons
S03B - ISAM DATASET TO BE PROCESSED, BUT NOT CREATED OR ITS DCB
NOT CLOSED AFTER CREATION.
--POSSIBLE CUASE--
DATASET WAS TO BE WRITTEN ON BUT WAS OPENED AS INPUT
LRECL/BLKSIZE PROBLEM EXISTS - INVALID VALUES OR NOT MULTIPLES

Only thing i could understood from the above messages is the LRECL one. I thought this might be the problem with the LRECEL, so i have coded all the optional parameters(lrecl,recfm,blksize) in my assembler program though as per book its not needed, but still the problem exists. So i understood it certainly not the problem.
I couldn't understand what does the line "ITS DCB NOT CLOSED AFTER CREATION" means. If that is the reason, can some one please tell how to check that and how to rectify it?

I'm just a beginner, so please bare with me for any of my mistakes. Please let me know if you need further info.