{"p":"can-20","op":"mint","tick":"can","amt":"1000","rows":[{"df":"qa","content":[{"q":"The backup operations before blockchain upgrading include the following contents:","a":"Block index backup: The block index is an important part of the blockchain database, which  includes key data such as header information and transaction hashes of all blocks. Before the upgrade, the block index needs to be backed up to ensure a smooth recovery during the upgrade process."}]}]}