Guardian Procedure Calls Reference Manual

procedure for that file. If file sync block checkpointing is performed, FILE_GETINFO_ returns
(in its last-error parameter) the status of the call to GETSYNCINFO (usually, last-error
= 0).
• Unable to communicate with backup
If an "unable to communicate with backup" error (that is, status.<0:7> = 1) occurs, this
normally indicates either that the backup process does not exist or that a system resource
problem exists. If a system resource problem exists, the checkpoint message to the backup is
probably too large.
• Invalid parameter
If you attempt to checkpoint the data area in the region used by the CHECKMONITOR
procedure in the backup process, then CHECKPOINT returns an "invalid parameter" error
(that is, status.<0:7> = 3). See the recovery procedure in the CHECKMONITOR procedure
Considerations (page 139).
• Takeovers and selectable segments
The selectable segment put into use following takeover depends on several factors:
◦ The segment in use at the time of the last checkpoint is put into use if it is available; that
is, the segment was allocated to the backup using the SEGMENT_ALLOCATE_CHKPT_
or CHECKALLOCATESEGMENT procedure and has not since been deallocated by the
SEGMENT_DEALLOCATE_CHKPT_ or CHECKDEALLOCATESEGMENT procedure.
◦ The segment in use when the CHECKMONITOR or CHECKSWITCH procedure was called
is used if the segment in use at the time of the last checkpoint is no longer available.
◦ No segment is used if the segment in use at the time of the last checkpoint and the segment
in use when the CHECKMONITOR or CHECKSWITCH procedure was called are both
unavailable.
• Increased file limits for key-sequenced files
The CHECKPOINT procedure can checkpoint the file synchronization blocks of file numbers
passed to it in the count-n parameters. In H06.28/J06.17 RVUs with specific SPRs and later
RVUs, the limits of the following file attributes for format 2 key-sequenced files can be increased,
which can result in file synchronization blocks with larger maximum sizes. (For a list of the
required H06.28/J06.17 SPRs, see SPR Requirements for Increased Enscribe Limits for the
H06.28/J06.17 Release (page 31).)
◦ The file synchronization blocks support synchronization IDs for a maximum of 127
partitions of an enhanced key-sequenced file; earlier RVUs only support a maximum of
64 partitions.
◦ The maximum key size for format 2 legacy key-sequenced files and enhanced
key-sequenced files is 2048 bytes, and the current key is part of the file synchronization
block; earlier RVUs only support a maximum key length of 255 bytes.
As a result of these increased limits, more memory may be required to checkpoint file
synchronization blocks, which can potentially reduce the number of file opens that can be
checkpointed in a single CHECKPOINT call and cause “message too large” errors to occur
at lower thresholds than previously.
144 Guardian Procedure Calls (C)