# How to use the 'OverrideCycles' setting in the Run Planning User Interface
**Background**
The OverrideCycles setting is used to change the way a read or part of read is treated by BCL Convert. The BCL Convert app for onboard DRAGEN or BaseSpace requires a v2 sample sheet, which can be made using Run Planning on select platforms or in BaseSpace. See [Sample Sheet page](https://help.connected.illumina.com/run-set-up/overview) for links to additional details on required and optional field inputs for v2 Sample Sheets.
*Key arguments for Override Settings*
* **Y** - Use data in Read cycles
* **U** - Use data as UMI cycles
* **I** - Use data as Index cycles
* **N** - Do not use data in either Read or Index
*Setting Override Cycles in Run Planning*
* The Run Planning UI is available in the Control Software on the MiSeq i100 Series and NovaSeq X Series instruments.
* BaseSpace allows for 'OverrideCycles' designation during the Run Planning sample sheet setup.
Run Planning with Onboard DRAGEN
Run Planning with BaseSpace
* The 'OverrideCycles' defaults in Run Planning will match the run setup as applicable: Y(Read 1); I(Index 1); I(Index 2): Y(Read 2).
To skip cycles in either the Read or Index:
* Designate the appropriate cycles with the mask flag "N."
* For example, mask the first cycle of each Read for Illumina Stranded RNA libraries using N1Y150 for Reads 1 and 2.
If the Index read includes a UMI portion:
* Designate the appropriate cycles with the UMI flag "U."
* For example, a run may have Index 1 with a UMI of 8 bases in a run setup of Read 1 150, Index 1 16, Index 2 8, Read 2 150. The Override Cycles would register as Y150;U8I8;I8;Y150.
To ignore an entire index while demultiplexing:
* Use case includes demultiplexing runs that contain both single-indexed and dual-indexed samples
* Remove the "I" from the 'OverrideCycles' setting for the index read that is to be ignored in the **\[BCLConvert\_Settings]** section.
* Remove the column (including the column header) for the index read that is to be ignored in the **\[BCLConvert\_Data]** section.
*Notes for Manual Sample Sheet Modification*
* **\[Reads]** section: This must contain the cycle numbers designated in the RunInfo.xml file (including the cycles to be ignored or treated differently).
* **\[BCLConvert\_Settings]** section: This must contain the appropriate 'OverrideCycles' setting.
* In this example, a sequencing run was completed with 16 cycles for the i5 index, but the actual index for a subset of samples is only 8 bp.
* * For some instruments that specify the i5 index in the Reverse Complement orientation, the 'N' is at the beginning of the i5 index (example: Y150;I8;N8I8;Y150). For more information, see [Guidelines for reverse complementing i5 sequences for demultiplexing](/software/general/software-general-reference_material-list/000001800.md).
* **\[BCLConvert\_Data]** section: This section contains the correct indexes.
* If some index cycles are ignored/treated differently, then this section should contain the correct, shortened indexes.
* Ns are not recognized as wildcard characters.
More information about this setting can be found in the BCL Convert online help [page](https://support-docs.illumina.com/SW/BCL_Convert/Content/SW/BCLConvert/SampleSheets_swBCL.htm).
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