Update Procedure in Oracle

Source: Internet
Author: User

A while ago, I saw a specific process about delete operations. Today I accidentally saw another update operation process, which is interesting. Let's go and learn it!

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1. the user submits an update statement.

2. server process checks the memory cache

If there is no valid memory space, start dbwr and write the dirty data blocks not written to the disk in the cache.

II. If there is space available, read data from the disk

3. Update Data in the cache

I apply for a rollback segment entry to write old data into the rollback segment

II lock update data

Iii. Record the modification in the redo log buffer at the same time.

4. the user submits a commit

I SCN increase

II write the redo log buffer into the redo log file

III tell the user that commit is complete

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