# Single Threader

The Single Threader step executes a sequence of steps in a single thread. This can help you tune performance by limiting the number of threads/processors used.

Common use cases include:

* Reducing overhead in transformations with many steps (for example, less data passing and thread context switching).
* Sorting rows within a specific time frame or row count for near-real-time streaming.
* Processing data in chunks, pausing, and then continuing after reaching a chunk size.

For more background, see [White Paper on Single Threading in Pentaho Data Integration](http://www.ibridge.be/?p=200).

### General

| Field              | Description                                                                      |
| ------------------ | -------------------------------------------------------------------------------- |
| **Step name**      | Unique name of the step on the canvas. Default is **Single Threader**.           |
| **Transformation** | Sub-transformation to run in a single thread. Enter a path or select **Browse**. |

If you select a transformation that shares the same root path as the current transformation, PDI automatically replaces the common root with `${Internal.Entry.Current.Directory}`.

If you are working with a repository, specify the transformation by repository name; otherwise, specify the `.ktr` file path. |

### Options tab

![Single Threader Options tab](/files/Q2s3TZrT1DD9syJlEy3M)

| Option              | Description                                                                                                                                     |
| ------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------- |
| **Injector step**   | Step that satisfies the Mapping Input Specifications (for example, filename, type, length, and precision). Enter a step name or select **Get**. |
| **Retrieval step**  | Step from which data is retrieved. Enter a step name or select **Get**.                                                                         |
| **Batch size**      | Starts processing a chunk after N rows are received. Default is `100`. You can use **Batch time (ms)** instead.                                 |
| **Batch time (ms)** | Starts processing a chunk after the specified delay (instead of using **Batch size**).                                                          |

### Parameters tab

![Single Threader Parameters tab](/files/0A4LjAoMbTC2ux3sgBZf)

Use this tab to pass parameters to the sub-transformation.

| Option                                          | Description                                                                           |
| ----------------------------------------------- | ------------------------------------------------------------------------------------- |
| **Pass parameter values to sub transformation** | Passes all parameter values from the parent transformation to the sub-transformation. |
| **Parameter name**                              | Parameter name passed to the sub-transformation.                                      |
| **Fixed value**                                 | Parameter value. You can set it as:                                                   |

* a literal value (for example, `Sub transformation`)
* a variable or parameter (for example, `${Internal.Job.Name}`)
* a combination (for example, `${FILE_PREFIX}_${FILE_DATE}.txt`) | | **Get parameters** | Retrieves parameters defined in the sub-transformation. |


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