Fish thanks for explanation but ... it is different than results of my test.
I have access to z/VSE 6.1 and wrote the program in cobol, which inloop wruet 80 bytes records with increnebted counter and some text. I've declared two extents in JCL? for output file and run the program with different limit for the loop. If the count is low and records fillout only 1st extend, 2nd is not deined in VTOC. I count is bigger, and records cover more tracks, in VTOC are two extents? (on the samevolume). So it seems, that 2nd extend will be allocated only if number of records will exceed the one extent size.?
Declaration in JCL is like below, if you nedd I codein cobol, I can send it also (it's very simple). I know that it is "modern" z/VSE, but I don't think, taht base rukes changed.
Piotr
// ASSGN SYS001,A82
// DLBL?? TSTFILE,'VSE3.TEST.DATASET',2024/024,SD
// EXTENT SYS001,VSE001,1,0,960,2
// EXTENT SYS001,VSE001,1,1,970,15
// EXTENT SYS001,VSE001,1,2,962,2
