Communication between an Oracle DB instance and an ASM instance

Scenario One: DB instance Startup

1) The Rbal and ASMB processes of the DB instance are started.

2) The ASMB process of the DB instance communicates with the CSS, obtains the connection string needed to connect to the ASM instance, and obtains the basic information of the ASM Disk group.

3) The ASMB process of the DB instance passes the information obtained to the Rbal process of the DB instance, and the Rbal process notifies the ASMB process of the ASM file information it needs to access.

4) The ASMB process of the DB instance and the ASMB process communication of the ASM instance obtain the corresponding information.

5) The Rbal process of the DB instance accesses the corresponding ASM disk according to the information received and opens the appropriate ASM file.

6) The ASMB process of the DB instance sends the heartbeat information to the ASMB process of the ASM instance.

Scenario Two: Creating an ASM File

1) The Rbal process of the DB instance notifies the ASMB process of the files that need to be created.

2) The ASMB process of the DB instance communicates with the ASMB process of the ASM instance to obtain the required extent map information.

3) The Rbal process of the DB instance accesses the corresponding ASM disk and creates the file based on the information received.

Scenario Three: The database foreground process accesses data on a disk group

1) The database foreground process communicates with the o00<x> process of the DB instance, requesting the required information.

2) The o00<x> process of the DB instance creates a connection to the ASM instance and generates the O00<x> process on the ASM instance.

3) The o00<x> process of the ASM instance returns the required extent map information to the o00<x> process of the DB instance.

4) The o00<x> process of the DB instance returns the corresponding extent map information to the database foreground process.

5) The database foreground process converts the received extent map information into corresponding data files and data block information, accessing the corresponding data block.

The ASM instance is responsible for managing the disk group's metadata, and the real I/O operation is done by the process in the DB instance.

Communication between an Oracle DB instance and an ASM instance