Problem:

We have a host product from Innovation Software, IAM, which allows for very large VSAM datasets. Can we use Mainframe Express to access these host datasets?

Resolution:

Yes this can be done although we do not support this 3rd party software unconditionally. Since IAM files are not really VSAM on the host, MVS or z/OS, when Mainframe Express tries to find the host dataset via data Connect, we get catalog information returned saying the host dataset is QSAM, so the initial access will fail when the OPEN is issued from the user program. If you modify the MFE Catalog properties for that entry saying it is VSAM, then we will try our next access asking for a VSAM dataset of the name you specify. IAM will intercept the request and handle the rest of the I/O as if it were VSAM and your user program can OPEN, READ, WRITE and CLOSE the host IAM dataset.

To simplify this, the MFE administrator could run JCL such as the following so the MFE Catalog entries are populated with the desired dataset names. Then he/she can modify these entries defining them as VSAM. Now when the user program runs and the OPEN is issued, the datasets will be processed as VSAM (via Data Connect and IAM's interaction).

//IEFBR14  EXEC PGM=IEFBR14

//DD1      DD DSN=LORINCE.D1890626.PRINTIN,DISP=SHR

//DD2      DD DSN=LORINCE.D1890811.SORTIN,DISP=SHR

//DD3      DD DSN=LORINCE.D1868701.FB130,DISP=SHR

//DD4      DD DSN=LORINCE.D1855118.VLB60,DISP=SHR

//SYSOUT   DD SYSOUT=*

/*