In a message dated 8/8/2005 6:08:28 P.M. Central Daylight Time, [EMAIL PROTECTED] writes: >No; the 3390 is an FBA disk simulating CKD. That's what I get for trusting, but not verifying, IBM's technical publications. GC26-4573-03, IBM 3390 Direct Access Storage Introduction, says "All 3390 models store data using the count-key-data (CKD) record format." > I'm not aware of any IBM disk later than the 3350 that wasn't FBA under the covers. I don't usually look under the covers. I just read the technical doc. >Not with the advent of the 3375; they were all FBA. The computations >for track capacity should have tipped you off to that.
This is true. The formulas indicate an underlying unit of track storage somewhere around 32 bytes, if I remember correctly. But since the control units supported only CKD and ECKD commands for these quasi-CKD disks and did not support the official FBA command set that was used with the 3310 and 3370 real FBA devices, I assumed the devices were really CKD. Control units were doing more mapping than I realized. Bill Fairchild ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
