# Problem: Slow Region Merges

![`smart`](./student-guide/diagram/SlowRegionMerges_aa_001_20221017.png)
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- Region merge is slow
  - Adjust the merge-schedule-limit appropriately, and adjust the max-merge-region-keys/max-merge-region-size parameters according to the situation to meet the merge threshold condition
  - Enable cross-table region merge        
    - 3.0 version
      - TiKV: split-region-on-table is set to false and needs to be restart to take effect
      - PD: namespace-classifier set to “” or “default”
    - 4.0 and later
      - TiKV: Set split-region-on-table to false, need to be restart to take effect
      - PD: key-type is set to txn or raw, or key-type is set to table and also set enable-cross-table-merge to true
  - Reduce the patrol-region-interval to speed up the inspection region