BuildBackupRangeAndSchema gets KV range and schema of tables.

CheckBackupStorageIsLocked checks whether backups is locked.

NewBackupClient returns a new backup client.

WriteBackupDDLJobs sends the ddl jobs are done in (lastBackupTS, backupTS] to metaWriter.

DefaultSchemaConcurrency is the default number of the concurrent backup schema tasks.

MaxResolveLocksbackupOffSleep is the maximum sleep time for resolving locks.

Checksum is the checksum of some backup files calculated by CollectChecksums.

Client is a client instructs TiKV how to do a backup.

Schemas is task for backuping schemas.

ClientMgr manages connections needed by backup.

ProgressUnit represents the unit of progress.