TMF Planning and Configuration Guide (H06.05+)

Reconfiguring Transaction Limits
HP NonStop TMF Planning and Configuration Guide—540136-002
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Memory Usage Limits
If you change these limit values, the changes do not take effect until the next time TMF
is started.
Memory Usage Limits
Two configurable limits control memory usage by governing whether or not new
transactions are permitted to begin:
•
TMF library memory usage limit (per processor)
•
The TMP memory usage limit (per TMP process)
Each limit consists of a pair of configurable threshold values that, when reached,
trigger the disabling or reenabling of new transactions. You can change these limits
by using the ALTER BEGINTRANS command. Only members of the super group can
issue ALTER BEGINTRANS commands.
TMF Library Memory Usage Limit
The TMFLIBMEMTHRESH limit controls the percentage of extended segment
memory, per processor, being used by the TMF library (TMFLIB) at any given time.
The limit consists of an upper and a lower percentage. When the percentage of
extended segment memory allocated to the TMF library reaches the upper percentage,
new transactions are not allowed to begin in that processor. When this percentage
falls below the lower percentage, new transactions are once again permitted to begin
in the processor, provided all other conditions for reenabling exist. The upper
percentage must be greater than the lower percentage.
The default values are:
Upper percentage = 95%
Lower percentage = 90%
If you change these limit values, the changes take effect immediately.
TMP Memory Usage Limit
The TMPMEMTHRESH limit controls the percentage of extended segment memory
being used by the transaction management process (TMP) at any given time.
The limit consists of an upper and a lower percentage. When the percentage of
extended segment memory allocated to the TMP reaches the upper percentage, new
transactions are not allowed to begin in the system. When this percentage falls below
the lower percentage, new transactions are once again permitted to begin, provided all
Caution. If the starting of new transactions is disabled, applications could abort unless they
have been coded to handle that situation.
Caution. You should never set this limit to 100%. If the TMF library ever uses 100% of the
memory allocated to it, it fails.