VMS Help RMS, XABFHC *Conan The Librarian (sorry for the slow response - running on an old VAX) |
The file header characteristic XAB (XABFHC) contains file header information that is output by the Open service and the Display service. The Create service can output information in this XAB when it opens an existing file through use of the Create-if option. The only input field is the longest record length (XAB$W_LRL) field. The Create service uses this field when it creates a sequential file that does not use a fixed-length record format. Note that, for unshared sequential files or sequential files shared using the FAB$V_UPI option, the values in the end-of- file block (XAB$L_EBK), first free byte in the end-of-file block (XAB$W_FFB), and longest record length (XAB$W_LRL) fields correspond to the values at the time of the last Close or Flush service. The following table lists the symbolic offset, the size in bytes, and a brief description of each field. Offset Size Description XAB$B_ATR 1 Record attributes; equivalent to FAB$B_RAT XAB$B_BKZ 1 Bucket size; equivalent to FAB$B_BKS XAB$B_BLN 1 Block length XAB$B_COD 1 Type code XAB$W_DXQ 2 Default file extension quantity; equivalent to FAB$W_DEQ XAB$L_EBK 4 End-of-file block XAB$W_FFB 2 First free byte in the end-of-file block XAB$W_GBC 2 Default global buffer count XAB$L_HBK 4 Highest virtual block in the file; equivalent to FAB$L_ALQ XAB$B_HSZ 1 Fixed-length control header size; equivalent to FAB$B_FSZ XAB$W_LRL 2 Longest record length XAB$W_MRZ 2 Maximum record size; equivalent to FAB$W_ MRS XAB$L_NXT 4 Next XAB address XAB$B_RFO 1 File organization and record format; combines FAB$B_RFM and FAB$B_ORG XAB$L_SBN 4 Starting logical block number for the file if it is contiguous; otherwise this field is 0 XAB$W_ 2 Version limit for the file VERLIMIT
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