anchor.diff:  
   [source,console]
   --------------------------------------------------
  -POST my_source_index/_split/my_target_index
  +POST /my_source_index/_split/my_target_index
   {
     "settings": {
       "index.number_of_shards": 5 <1>
  
positive.code: old and new indices have respectively +M+ and +N+ shards, this has no overhead
  compared to searching an index that would have +M+N+ shards.
  
  [float]
  ==== Preparing an index for splitting
  
  Create a new index:
  
  [source,console]
  --------------------------------------------------
  PUT my_source_index
  {
    "settings": {
      "index.number_of_shards" : 1
    }
  }
  --------------------------------------------------
  
  In order to split an index, the index must be marked as read-only,
  and have <<cluster-health,health>> `green`.
  
  This can be achieved with the following request:
  
  [source,console]
  --------------------------------------------------
  PUT /my_source_index/_settings
  {
    "settings": {
      "index.blocks.write": true <1>
    }
  }
  --------------------------------------------------
  // TEST[continued]
  
  <1> Prevents write operations to this index while still allowing metadata
      changes like deleting the index.
  
  [float]
  ==== Splitting an index
  
  To split `my_source_index` into a new index called `my_target_index`, issue
  the following request:
  
  [source,console]
  --------------------------------------------------
  POST my_source_index/_split/my_target_index
  {
    "settings": {
      "index.number_of_shards": 2
  
negative.code: become `active`. At that  point, Elasticsearch will try to allocate any
  replicas and may decide to relocate the primary shard to another node.
  
  
  [[split-wait-active-shards]]
  ==== Wait for active shards
  
  Because the split operation creates a new index to split the shards to,
  the <<create-index-wait-for-active-shards,wait for active shards>> setting
  on index creation applies to the split index action as well.
  
  
  [[split-index-api-path-params]]
  ==== {api-path-parms-title}
  
  `<index>`::
  (Required, string)
  Name of the source index to split.
  
  include::{docdir}/rest-api/common-parms.asciidoc[tag=target-index]
  
  
  [[split-index-api-query-params]]
  ==== {api-query-parms-title}
  
  include::{docdir}/rest-api/common-parms.asciidoc[tag=wait_for_active_shards]
  
  include::{docdir}/rest-api/common-parms.asciidoc[tag=timeoutparms]
  
  
  [[split-index-api-request-body]]
  ==== {api-request-body-title}
  
  include::{docdir}/rest-api/common-parms.asciidoc[tag=target-index-aliases]
  
  include::{docdir}/rest-api/common-parms.asciidoc[tag=target-index-settings]
  