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Tip: Tivoli Storage Manager can use the parameter SELFTUNEbufpoolsize
YES in the server options file to activate self-tuning. When you activate this
option, the server will check the cache hit ratio each time inventory expiration
is run. If the value is less than 98%, then it will increase the BUFPOOLSIZE by
a predictable factor related to the actual cache hit ratio achieved. An upper
limit for BUFPOOLSIZE with self-tuning is imposed of 10% of the real memory
for AIX, HP UX, Solaris, Linux, and Windows, and 50% of the region size in
z/OS. If you still need a larger BUFPOOLSIZE and it is acceptable in your
environment, you will have to set the value manually.
MIRRORWRITE
This specifies how mirrored volumes are accessed when the server writes pages
to the recovery log or database during normal processing. A value of
specifies that the server writes to the mirrored volume one after another. Server
performance decreases because a successful I/O must occur before the next
write can occur. A value of
volumes in parallel. This mode allows all mirrors to obtain the new page at
approximately the same time.
Note: If a system outage occurs at exactly the instant that each mirror is
partially complete in writing its page, a partial write to each mirror could result.
See the DBPAGESHADOW option below to prevent this.
When using mirrored database volumes in sequential mode, using a disk system
with write caching ability can improve database performance. When writing in
sequential mode, one database volume write must complete before the mirror is
written to. A disk system with write cache allows the mirror to be written to almost
instantaneously, nearly doubling the amount of write activity possible. Many disk
systems can do this; however it may need to be specifically enabled. Check your
disk vendor's documentation for details.
DBPAGESHADOW
This specifies whether database page shadowing is enabled. If database page
shadowing is enabled, Tivoli Storage Manager mirrors every write to a database
page. This mirror is represented by a shadow file that contains these written
mirrors. DBPAGESHADOW YES eliminates the requirement to set
MIRRORWRITE SEQUENTIAL to prevent exposure to partial page writes. We
recommend keeping the default of YES.
Database reorganization
Over time, database volumes can become fragmented. You can restore the
efficiency of the database and improve database performance by reorganizing
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IBM Tivoli Storage Manager Implementation Guide
parallel
specifies that the server writes to all mirrored
sequential
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