Performance Tuning Guide - EMC Community Network

Designing the Application
Managing group memberships
The number of groups tends to increase with the number of objects in an application. When users
belong to more than 250 groups, a threshold is reached and the DQL changes to accommodate the
number of groups they are in, which results in degraded performance.
The following DQL statement gets a count from the dm_process object:
select count(r_object_id) as c from dm_process (all) where r_object_id in
('4b0011ec8005c985','4b0011ec800af4fd','4b0011ec8000431a','4b0011ec80004319')
and any sd_element_type = '080011ec8007d38b' and any sd_element_type = '080011ec800042d9'
When the user belongs to 249 groups, the above DQL takes 0.032 seconds. When a user belongs to 251
groups, the above DQL takes 12.688 seconds (almost 400 times slower). The performance impact of
belonging to 250 or more groups affects most TaskSpace operations involving user object requests.
In addition to the 250 group membership threshold performance affect, every session the user creates
caches the groups for which the user is a member. When many users belonging to many groups use
the system, Content Server becomes consumed with caching groups for every new session, becomes
unable to service other requests, and the application can shut down.
Working around the 250 group threshold
The 250 group membership threshold can be overridden by setting the group limit environment
variable to something higher than 250, before hitting the 250 group threshold. Setting the group
limit parameter maintains the behavior of the DQL for less than 250 groups, until the specified
group limit is hit.
For example, using DM_GROUP_LIST_LIMIT=1,000, the query behavior stays the same until the
user has over 999 groups. Set the group limit as an operating system parameter on the Content Server
and restart Content Server for the setting takes effect. Figure 20, page 54 shows how the setting looks
in a Windows environment.
EMC Documentum xCP 1.0 Performance Tuning Guide 53