[[tsds-index-settings]]
=== Time series index settings

Backing indices in a <<tsds,time series data stream (TSDS)>> support the
following index settings.

[[index-mode]]
`index.mode`::
preview:[] (<<_static_index_settings,Static>>, string) Mode for the index.
Valid values are <<time-series-mode,`time_series`>> and `null` (no mode).
Defaults to `null`.

[[index-time-series-start-time]]
`index.time_series.start_time`::
preview:[] (<<_static_index_settings,Static>>, string) Earliest `@timestamp`
value (inclusive) accepted by the index. Only indices with an `index.mode` of
<<time-series-mode,`time_series`>> support this setting. For more information,
refer to <<time-bound-indices>>.

[[index-time-series-end-time]]
`index.time_series.end_time`::
preview:[] (<<dynamic-index-settings,Dynamic>>, string) Latest `@timestamp`
value (exclusive) accepted by the index. Only indices with an `index.mode` of
`time_series` support this setting. For more information, refer to
<<time-bound-indices>>.

[[index-look-ahead-time]]
`index.look_ahead_time`::
preview:[] (<<_static_index_settings,Static>>, <<time-units,time units>>)
Interval used to calculate the `index.time_series.end_time` for a TSDS's write
index. Defaults to `2h` (2 hours). Accepts `1m` (one minute) to `7d` (seven
days). Only indices with an `index.mode` of `time_series` support this setting.
For more information, refer to <<tsds-look-ahead-time>>. Additionally this setting
can not be less than `time_series.poll_interval` cluster setting.

[[index-routing-path]] `index.routing_path`:: preview:[]
(<<_static_index_settings,Static>>, string or array of strings) Plain `keyword`
fields used to route documents in a TSDS to index shards. Supports wildcards
(`*`). Only indices with an `index.mode` of `time_series` support this setting.
Defaults to the list of <<time-series-dimension,dimension fields>> with a
`time_series_dimension` value of `true` defined in your component templates. For
more information, refer to <<dimension-based-routing>>.

[[index-mapping-dimension-fields-limit]]
// tag::dimensions-limit[]
`index.mapping.dimension_fields.limit`::
preview:[] (<<dynamic-index-settings,Dynamic>>, integer)
Maximum number of <<time-series-dimension,time series dimensions>> for the
index. Defaults to `16`.
// end::dimensions-limit[]