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FAQ: What is the impact of increasing the ArcSDE server configuration parameter 'TLMINTERVAL'?

Question

What is the impact of increasing the ArcSDE server configuration parameter 'TLMINTERVAL'?

Answer

The ArcSDE configuration parameter TLMINTERVAL controls the time interval, in seconds, when the gsrvr process queries the ArcSDE table, sde_tables_modified, to discover if any objects in the ArcSDE repository have been modified.

The sde_tables_modified table maintains information on the last date each of the sde repository tables have been modified.

For example, each time a table is created, an entry in the table_registry for the new table is inserted. After the table_registry is modified, the entry for time_last_modified in the sde_tables_modified is updated to reflect the moment when the table_registry table was modified.

The information for when an ArcSDE table was last modified is very important for maintaining cached information in each ArcSDE gsrvr (connection) process. Before the gsrvr executes any queries, it first must verify that the information in its local cache (properties about tables and layers) is consistent. To validate that the cache is consistent, the gsrvr must compare all the dates from the sde_tables_modified table with the dates for each object in the cache. If the gsrvr discovers that any of the ArcSDE repository tables have been modified since the cache was created, the cached information for the object being queried is discarded and re-obtained by querying the ArcSDE repository.

The default value for TLMINTERVAL is 1 second. The value represents the interval in which the gsrvr process queries the ArcSDE table, sde_tables_modified, to validate its cache. The larger the TLMINTERVAL value, the longer the time between queries for validating the cache.

If an organization knows their data model is static and that there are no changes that update the ArcSDE repository, then the TLMINTERVAL value can be increased to a large value. By increasing the value, each gsrvr executes fewer queries against the sde_tables_modified table to validate its cache (improving performance).

If the organization is knowingly changing their data model, creating new tables, layers or modifying existing tables, which causes the ArcSDE repository to be updated, then it is not recommended to increase the TLMINTERVAL value.

The consequences of increasing the TLMINTERVAL value and making changes in the organization's data model can lead to situations where existing connections are unable to view newly created tables and layers in the ArcSDE instance.

For example, if the TLMINTERVAL is set to 1000 seconds and a user creates a new layer with a geoprocessing command, that user's session and existing connected sessions will not be able to access the new layer (by way of the add data dialog box in ArcGIS) until their session's gsrvr cache has been invalidated after 1000 seconds has elapsed.

Therefore, it is very important to understand the organization's workflow prior to changing the value for the TLMINTERVAL parameter.

Note:
For additional information on the ArcSDE configuration parameter TLMINTERVAL, reference the documentation in the Administration Command Reference, provided with the ArcSDE installation.