HP Raining DataCorp. mvEnterprise - Manual (Page 30)

Page 28 mvEnterprise Release 4.1 on AIX Installation Guide
1.11 mvEnterprise Disk Flushing Program
This program is available on the AIX systems, and would normally
replace the native system syncd or fsflush daemons (background
processes). The program is mvEnterprise machine specific and performs
as follows:
· The mvEnterprise database is divided into two segments; the space
above the system file base (SYSBASE) and the space below it,
enabling aggressive flushing of the data frames (those located above
SYSBASE). Flushing of the workspace frames (below SYSBASE) is
unnecessary.
· The data space is divided into approximately equal sections (slices).
Each section on a single drive is mmaped and flushed to disk. The
disk flusher then sleeps a prescribed amount of time and then
continues to the next section on the next disk drive.
· This process allows flushing of the entire file system data space in
approximately in n x m (where n equals the number of sections and
m equals the sleep time in seconds). The defaults for the program
are 60 sections and a one-second sleep, so the data space is
synchronized to disk approximately once per minute.
NOTE: The workspace below SYSBASE is not normally synchronized
(synced) since it contains no useful data in the event of a system
crash.
· After completing a number of data space flush cycles (loops), the
program attempts to sync first the entire mvEnterprise virtual
machine and finally the entire system. The last step is necessary
because the user may have terminated the standard AIX synced
process.
· The act of syncing the entire machine may create the same
performance problems the user is attempting to avoid. To minimize
this possibility, most of the system should already be flushed before
issuing the sync request. The program performs the following tasks:
·
·
·
·
Changes the sleep setting on the last pass through the data
frames to a much smaller value.
Syncs sections of the work space using this smaller sleep
time.
Executes fsync (an AIX system call) on the mvEnterprise
file systems with the smaller sleep time.
Issues the system wide sync.