oracle lock mode

By v$lock, we could have a look at lock in every session. Lock have a lot of mode:

mode|name||desc
–|–||–
0|none|
1|null|
2|Row-S||row sharing lock: share row
3|Row-X||row exclusive lock: for modify row
4|Share||share lock: block other DML
5|S/Row-X ||shared row exclusive lock: block other transaction
6|exclusive||exclusive lock: independently access and use

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lock type:

• TM lock for parallel accessing table
• TX transaction lock or row lock for parallel accessing row
• MR media recover lock means database online
• ST space transaction lock means due to bad file structure, some segments in database in increase or shrink SMON or merging free space nearby.