NetBase for MPE Reference Guide

NetBase Shadowing
5-35
The program may be run with alternate entry points to provide optional features. If the program is
run with the WAIT entry point specified, the posting process sends a message back to NBFLUSH
before terminating. If any of the processes that propagate the message between NBFLUSH and the
posting process are down, an error message is returned to NBFLUSH. This works slightly differently
if shadowing is being performed using IMAGE log files. First, use the alternate entry point
CHECKPOINT or CHECKWAIT. Second, the name of the log file as it appears in the directory should
be passed in the INFO string. Also, NBFLUSH does not terminate until the log file has been
completely read and the process for that log file has stopped.
The CHECKWAIT entry point is valid only if shadowing is being performed using IMAGE log files.
It can be used to check that the updates for a particular process have completed. In this case, the
flush message is passed to the posting process only when all records have been read that were
written to the log file up to the time that NBFLUSH was run.
Running NBFLUSH with the STOP or STOPWAIT entry points is used to flush updates to all the
shadow copies on a particular node and stop the posting process. This operates much the same as
flushing updates to one particular file, the difference being that the posting process is directed to
stop itself after the stop record is received. This option is commonly used prior to performing a
backup of the shadow copy of files since it ensures that all updates are posted, relative to the time
that NBFLUSH was run, and it directs the posting process to stop, thus freeing the files for the
backup. This also causes all subsequent updates to the master files to be queued until the backup is
complete and the posting process restarted.
The QUIET and QUIETWAIT entry points work just like the STOP/STOPWAIT entry points except that
NBPOST stops only when the count of DBX transactions has reached zero (no DBX transactions in
process). This option needs to be enabled by the NBCTRL, CONFIG option of SHADOW - Enable Quiet
Period Flush.
Note: The counts are stored in the file TICOUNTS.DATA.NETBASE. If something goes
wrong with the counts, this file can be purged. If a sync error is detected, this feature
will disable itself.