Cache expiration policies

In
FactoryTalk
, rules for directory cache expiration are managed system-wide by the
Directory Protection Policy Settings
security policy properties. These policies determine:
  • How long cache files remain available after the client computer disconnects from the server
  • If a warning displays before the directory cache expires
Directory cache expiration policies for a specific computer or group of computers can be customized. For example, to allow a group of laptop computers to operate without a network connection for a longer time period, and for the cache to never expire for one of the laptops. To override the
FactoryTalk
 network directory cache expiration policies, set directory cache timeout policies for a computer group or an individual computer.
The directory cache timeout policies cannot be modified in a
FactoryTalk
 local directory.
TIP:
The directory cache timeout policies are not supported if the client computer is installed with
FactoryTalk Services Platform
 version 2.40 or earlier.
The cache expiration policies in
FactoryTalk
 are applied in this order of precedence:
  • By default, all computers in the directory adopt the directory cache expiration policy.
  • Computer group cache expiration policies take precedence over the directory cache expiration policy. If a computer is assigned to multiple computer groups, the computer adopts the cache expiration of the first assigned computer group in alphabetical order.
  • Computer cache expiration policies take precedence over the directory cache expiration policies of any of its computer groups.
This example shows how the cache expiration policies work.
Suppose that:
  • Three computers connected to the
    FactoryTalk
     network directory server. MYLAPTOP is a member of computer group Laptops. MYWORKSTATION is a member of computer group Workstations.
    Example_Computers_and_Groups
The current setting covers the majority of your computers. Optionally, customize specific settings for some cases. For example, to allow computers of Laptops to operate in a disconnected state for a longer period (for example, 7 days, that is, 168 hours). Also, turn off the cache expiration functionality for computer
MYSERVER
.
To achieve these results,
  • In the computer group policy setting of Laptops, select to override the directory cache expiration policy and set the computer group cache expiration value to
    168
    .
  • In the computer policy setting of
    MYSERVER
    , select to override the directory cache expiration policy and set the computer cache expiration value to
    0
    .
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