Monday, July 12, 2010

DB2 agent works in depth with the connection process



Introduction

DB2 agent (agent) is in the DB2 server service application requests a number of processes or threads. When an external application to connect to DB2 instance access request made, DB2 agent will be activated to respond to these requests. General DB2 agent is known as job agents, job agents about three types: free agents, coordinate the activities of agents, sub-agents.

鈼?free agent: refers to any task agent. This agency does not serve any remote connection does not serve the local connection, in a backup or standby state.

鈼?agency coordination of activities: means the agent is in working condition, each produced by an external application has a database of activities connected to the coordination of activities to the agency it serves.

鈼?sub agency: refers to the coordination agent to accept the work of distribution out of the next level agency. In DB2 V95, only the multi-partition environment (MPP) or a node within the parallel environment (SMP) under which there is sub-agents, in DB2 V95 in all circumstances there may be sub-agent.

DB2 server in a proxy pool, when the instance starts here just have a number of agents (their number depends on the instance of the parameter NUM_INITAGENTS). In the absence of any database connection, they are in standby, is free agency. When there is an external program to connect to the database, the agency began to receive orders to serve in these new connections, then they become the coordination of activities agents. The coordination agent then the gradual breakdown of the request, under an agency that is assigned to the sub-agent to deal with. If the current agents are already working at the same time again a new request, the database manager will generate a new proxy to answer. When the transaction is completed and the database connection is lost, the coordinating agent or to return back into free agent pool agents, or automatically disappear (depending on the instance of the parameter NUM_POOLAGENTS). This is an agency of the life cycle.

Related configuration parameters

Through the implementation of DB2 get dbm cfg and agents can see several examples of related parameters: MAXAGENTS, NUM_POOLAGENTS, NUM_INITAGENTS, MAX_COORDAGENTS, MAX_CONNECTIONS, MAXCAGENTS. The following brief description on what they do:

鈼?MAXAGENTS: This parameter for the current instance of the number of all agents, including the coordination of agents, free agents and sub agents combined. However, in this parameter in the DB2 V95 is no longer used.

鈼?NUM_POOLAGENTS: This parameter is used to control the agent pool, the number of idle agents. When the activities of the agency to complete its work back to become a free agent when the agent pool, if more than this parameter, then the agent will automatically disappear. NOTE: In connection concentrator enabled case, the pool of free agents the number of agents at a time may exceed the size of NUM_POOLAGENTS to deal with unexpected high-density connection.

鈼?NUM_INITAGENTS: This parameter is the instance mentioned above when they just started generating some number of free agents. This is to improve performance, because these agents can always become a coordinated response to external application to request agents, instead of the temporary re-generate a new agent.

鈼?MAX_COORDAGENTS: This parameter determines the instance of the largest coordinated at the same time the number of agents (in a multi-partition environment, a node refers to the maximum number of coordinating agents).

鈼?MAX_CONNECTIONS: This parameter determines the instance to allow connection to a maximum number of connections (in a multi-partition environment, a node refers to the maximum number of connections).

鈼?MAXCAGENT: This parameter determines the number of instances of the token, a coordinating agency can only be a token to the service application. If not token, the coordinating agency can only wait. However, in this parameter in the DB2 V95 has also canceled.







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