Guardian Programming Reference Summary for C

CONTROL Operations
Guardian Programming Reference Summary for C—522630-001
9-4
21 Disk, allocate or deallocate extents. (Write
access is required.)
0: deallocate all extents
past the end-of-file extent
1: <maximum-
extents> number of
extents to allocate for a
nonpartitional file (for DP2
disk files only)
1:16* number of partitions
number of extents to
allocate for a partitioned
file
22 Cancel an AM3270 I/O operation. None
24 Magnetic tape, force end-of-volume (EOV).
Next volume in set is requested and current
volume is unloaded.
Valid only for ANSI or IBM label tape.
None
26 Requests immediate completion of all
outstanding I/O requests without loss of data by
the recipient of the CONTROL 26 request.
None
27 Wait for DP2 disk file write.
This operation finishes when a WRITE, WRITEUPDATE, or
WRITEUPDATEUNLOCK occurs on a DP2 disk file designated by
<filenum>. Not valid for partitioned files.
Do not assume that the file contains any new data when a call to CONTROL 27
finishes; assume only that it is time to check the file for new data.
CONTROL 27 also finishes when a WRITE or WRITEUPDATE occurs as part
of a logical undo of a transaction by the backout process or when a volume
goes down.
If SETMODE 146 was specified, each write completes only one CONTROL
27; otherwise, each write completes all pending CONTROL 27 operations.
To ensure that no updates are missed, you should issue a nowait CONTROL 27
call on one open to a file, then read data from the file on another open, and
finally wait for the CONTROL operation to finish. If CONTROL 27 were
executed after reading, a write by another process could occur between the read
and the CONTROL operations. The file open that is used for the CONTROL
operation should have a <syncdepth> of 0. Path errors and network errors
might indicate successful completion.
Refer to the discussion of CONTROL operation 27 in the Guardian
Programmer’s Guide.
Table 9-2. CONTROL Operations 2 - 27
Operation Description Description of <param>