# Class Transaction
[View code](https://github.com/sequelize/sequelize/blob/2c4a9f3cf9887fb33c31e397e758dd4aa3374d01/lib/transaction.js#L19)
The transaction object is used to identify a running transaction. It is created by calling `Sequelize.transaction()`.
To run a query under a transaction, you should pass the transaction in the options object.
**Params:**
| Name | Type | Description |
| ---- | ---- | ----------- |
| sequelize | Sequelize | A configured sequelize Instance |
| options | Object | An object with options |
| options.autocommit=true | Boolean | Sets the autocommit property of the transaction. |
| options.isolationLevel=true | String | Sets the isolation level of the transaction. |
| options.deferrable | String | Sets the constraints to be deferred or immediately checked. |
***
## `ISOLATION_LEVELS`
[View code](https://github.com/sequelize/sequelize/blob/2c4a9f3cf9887fb33c31e397e758dd4aa3374d01/lib/transaction.js#L71)
Isolations levels can be set per-transaction by passing `options.isolationLevel` to `sequelize.transaction`.
Default to `REPEATABLE_READ` but you can override the default isolation level by passing `options.isolationLevel` in `new Sequelize`.
The possible isolations levels to use when starting a transaction:
```js
{
READ_UNCOMMITTED: "READ UNCOMMITTED",
READ_COMMITTED: "READ COMMITTED",
REPEATABLE_READ: "REPEATABLE READ",
SERIALIZABLE: "SERIALIZABLE"
}
```
Pass in the desired level as the first argument:
```js
return sequelize.transaction({
isolationLevel: Sequelize.Transaction.SERIALIZABLE
}, function (t) {
// your transactions
}).then(function(result) {
// transaction has been committed. Do something after the commit if required.
}).catch(function(err) {
// do something with the err.
});
```
***
## `LOCK`
[View code](https://github.com/sequelize/sequelize/blob/2c4a9f3cf9887fb33c31e397e758dd4aa3374d01/lib/transaction.js#L115)
Possible options for row locking. Used in conjuction with `find` calls:
```js
t1 // is a transaction
t1.LOCK.UPDATE,
t1.LOCK.SHARE,
t1.LOCK.KEY_SHARE, // Postgres 9.3+ only
t1.LOCK.NO_KEY_UPDATE // Postgres 9.3+ only
```
Usage:
```js
t1 // is a transaction
Model.findAll({
where: ...,
transaction: t1,
lock: t1.LOCK...
});
```
Postgres also supports specific locks while eager loading by using OF:
```js
UserModel.findAll({
where: ...,
include: [TaskModel, ...],
transaction: t1,
lock: {
level: t1.LOCK...,
of: UserModel
}
});
```
UserModel will be locked but TaskModel won't!
***
## `commit()` -> `this`
[View code](https://github.com/sequelize/sequelize/blob/2c4a9f3cf9887fb33c31e397e758dd4aa3374d01/lib/transaction.js#L127)
Commit the transaction
***
## `rollback()` -> `this`
[View code](https://github.com/sequelize/sequelize/blob/2c4a9f3cf9887fb33c31e397e758dd4aa3374d01/lib/transaction.js#L148)
Rollback (abort) the transaction
***
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