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System Architecture

When OnLine is initialized, all page-cleaner daemons are started and placed
in idle mode. As master daemon, tbinit directs each tbpgcl to an

LRU

queue

of shared-memory buffers. (Refer to

 for more information about

the

LRU

 queues.) Periodically, tbpgcl wakes and searches through the

LRU

queues, looking for buffers that need to be flushed. (Refer to

information about the

LRU

 queues and buffer flushing.)

Page-cleaner daemons (or the tbinit daemon) also perform the flushing
required during a checkpoint when OnLine shared-memory data is synchro-
nized with the data stored on disk. (Refer to

for further information

about checkpoints.)

The recommended number of page-cleaner daemons is one daemon for each
disk dedicated to OnLine. The maximum number of page-cleaner daemons
permitted in OnLine is 32. (Refer to

 for further information on

tuning the value of

CLEANERS

 to improve performance.)

The state of each page-cleaner daemon is tracked in the page-cleaner table in
shared memory and can be displayed with the command tbstat -F. (Refer to

 for further information about monitoring page-cleaner activity

with tbstat -F.)