Oracle DML operation process

The user transmits the DML operation statement to the buffercache in sga through the process, and then updates the changed data block in the buffercache.

The user transmits the DML operation statement to the buffer cache in the sga through the process, and then updates the changed data block in the buffer cache.

DML operations. All Oracle processes are executed together!

The user transmits the DML operation statement to the buffer cache in the sga through the process, and then updates the changed data block in the buffer cache, then, the logwr process first transmits the database before the operation to the undo, and transmits the operation data to the redo. This process is faster (the redo log is a continuous write)

The dbwn process then writes the dirty data blocks in the buffer cache to the data file at an interval determined by the ckpt process.

The ckpt process runs as follows:

Write the control file and data header file once every 3 seconds or more frequently, and record the location (SCN (system change number) of the block that DBWN writes to the disk from SGA)

Then, the ckpt process immediately notifies the dbwn process after each execution to write the existing dirty data blocks to the data file.

When the dbwn process writes dirty data blocks to the data file, a checkpoint is generated)

Then ckpt updates the scn to the scn in the header file of the control file and data file, continue to notify dbwn to write the dirty data blocks in the buffer cache to the data file and dbwn to create a checkpoint and then wait for the notice of the ckpt Process

This cycle is the process of oracle dml operations!

Supplement later:

Introduction by another netizen:

1. Start the transaction;

2. Find the required data block in the buffer cache. If no data block is found, load it into the buffer cache from the data file;

3. The transaction modifies the buffer cache data block. The data is identified as "dirty data" and written into the log buffer;

4. transaction commit. The LGWR process writes the "dirty data" in the log buffer to the redo log file;

5. When a checkpoint occurs, the CKPT process updates the information in the file header of all data files, and the DBWn process writes the dirty data in the Buffer Cache to the data file.

Note: checkpoint: The ckpt process triggers oracle to perform the checkpoint action, and dirty blocks in the data buffer are written in redo records but not written to datafile) the contents are written to the data file and the site space is released. It is completed by the dbw background process and the scn of controlfile and datafile is modified.
In general, manual execution (alter system checkpoint) is because you want to delete a log, but the log does not have content synchronized to the data file, you need to manually check the point to synchronize data, then you can drop logfile group n.

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