What happened in the background while taking backup in DB2?
What happened in the background while taking backup in DB2?
As we all know in db2 architecture EDUs play a vital role, same here also. In backup process model EDUs like db2agents, db2bm & db2med will be there. If the backup uses a storage manager an additional process called db2vend will be created.
The db2agents EDU dose most of its work during the start of backup and then waits for the backup to be completed.
db2agent performs the below tasks:
1.Calculate and create an optimal number of db2bm and db2med EDUs
2.Allocate an optimal number of optimally sized backup buffers
3.Display the selected tunable values to the db2diag.log
4.Allocate message queues for inter-EDU communication
5.Create a list of table spaces that are sorted by decreasing size
6.Coordinate the backup process by sending control messages to the db2bm and db2med EDUs.
db2bm:
For each tablespace there will be one db2bm process which is going to capture the data and fills the empty queue and sends it to the backup buffer. Then sends the backup buffer to the backup device using db2med process.
db2med:
It is responsible for acquiring a backup buffer from the full queue and writing it to the backup device. It handles the I/O directly when it writes the buffers to disk, if it writes to the storage manager the db2vend process will be created and backup buffers will be sent to db2vend.
db2vend:
It is created by db2med EDU if a storage manager is being used.
The db2vend process receives a full buffer from the db2med and call the appropriate vendor API for sending data to the storage manager.