Page 100 - DCAP408_WEB_PROGRAMMING

Windows Programming

Notes  When an application connects to a database: In a partitioned database surroundings, in a
non-partitioned database with the database manager intra-partition parallelism
configuration parameter (intra_parallel) enabled, or in the surroundings in which the
connection concentrator is enabled, multiple applications can be assigned to application
groups to share memory. Every application group has its own allotment of shared memory.
In the application-group shared memory, each application contains its own application
control heap but utilizes the shared heap of the application group which enhances the
competence of cache and memory usage.
The following three database configuration parameters find out the size of the application
group memory:
 The appgroup_mem_sz parameter, which states the size of the shared memory for the
application group
 The groupheap_ratio parameter, which states the percent of the application-group
shared memory permitted for the shared heap

 The app_ctl_heap_sz parameter, which states the size of the control heap for every
application in the group.
The database manager configuration parameter max_connections fixes an upper limit on
the number of applications that can attach to a database. As each application that attaches
to a database includes the allocation of some memory, permitting a larger number of
concurrent applications will potentially make use of more memory.
To some extent, the maximum number of applications is also administered by the database
manager configuration parameter maxagents or max_coordagents for partitioned database
surroundings. The maxagents parameter fixes an upper limit to the total number of database
manager agents in a database partition. These database manager agents comprise active
coordinator agents, subagents, inactive agents, and idle agents.
If you are encountering memory errors when attempting to connect to a database, try
making the following configuration amendments:
 In a non-partitioned database environment with no intra-query parallelism enabled,
enlarge the value of the maxagents database configuration parameter.
 In a partitioned database environment or an environment where intra-query
parallelism is enabled, augment the larger of maxagents or max_coordagents.

 In surroundings where max_connections has been configured to a value that is
greater than max_coordagents, you can also augment max_connections to resolve
the error.
 When an agent is created: Agent private memory is assigned for an agent when the agent
is allocated as the consequence of a connect request or a new SQL request in a parallel
environment. Agent private memory is assigned for the agent and comprises memory
that is used only by this particular agent, like the sort heap and the application heap.

!
Caution When a database is already in use by one application, only agent private memory
and application global shared memory is assigned for consequent connecting applications.

The figure also states the following configuration parameter settings, which limit the amount of
memory that is assigned for every type of memory area. Observe that in a partitioned database
environment, this memory is assigned on each database partition.

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