diff --git a/cmd/dm-syncer/config.go b/cmd/dm-syncer/config.go
index b50143ae1b..6ecd71012d 100644
--- a/cmd/dm-syncer/config.go
+++ b/cmd/dm-syncer/config.go
@@ -16,13 +16,14 @@ package main
 import (
 	"flag"
 	"fmt"
+	"os"
+
 	"github.com/BurntSushi/toml"
 	"github.com/go-mysql-org/go-mysql/mysql"
 	"github.com/pingcap/errors"
 	bf "github.com/pingcap/tidb-tools/pkg/binlog-filter"
 	"github.com/pingcap/tidb-tools/pkg/filter"
 	router "github.com/pingcap/tidb-tools/pkg/table-router"
-	"os"
 
 	"github.com/pingcap/dm/dm/config"
 	"github.com/pingcap/dm/pkg/utils"
diff --git a/dm/master/bootstrap.go b/dm/master/bootstrap.go
index 1697c5cf48..13d5db0b13 100644
--- a/dm/master/bootstrap.go
+++ b/dm/master/bootstrap.go
@@ -162,13 +162,13 @@ func (s *Server) importFromV10x(ctx context.Context) error {
 }
 
 // collectSourceConfigFilesV1Import tries to collect source config files for v1.0.x importing.
-func (s *Server) collectSourceConfigFilesV1Import(tctx *tcontext.Context) (map[string]config.SourceConfig, error) {
+func (s *Server) collectSourceConfigFilesV1Import(tctx *tcontext.Context) (map[string]*config.SourceConfig, error) {
 	files, err := ioutil.ReadDir(s.cfg.V1SourcesPath)
 	if err != nil {
 		return nil, err
 	}
 
-	cfgs := make(map[string]config.SourceConfig)
+	cfgs := make(map[string]*config.SourceConfig)
 	for _, f := range files {
 		if f.IsDir() {
 			continue // ignore sub directories.
@@ -186,7 +186,7 @@ func (s *Server) collectSourceConfigFilesV1Import(tctx *tcontext.Context) (map[s
 			return nil, err
 		}
 
-		cfgs[cfgs2[0].SourceID] = *cfgs2[0]
+		cfgs[cfgs2[0].SourceID] = cfgs2[0]
 		tctx.Logger.Info("collected source config", zap.Stringer("config", cfgs2[0]))
 	}
 
@@ -195,7 +195,7 @@ func (s *Server) collectSourceConfigFilesV1Import(tctx *tcontext.Context) (map[s
 
 // waitWorkersReadyV1Import waits for DM-worker instances ready for v1.0.x importing.
 // NOTE: in v1.0.x, `count of DM-worker instances` equals `count of source config files`.
-func (s *Server) waitWorkersReadyV1Import(tctx *tcontext.Context, sourceCfgs map[string]config.SourceConfig) error {
+func (s *Server) waitWorkersReadyV1Import(tctx *tcontext.Context, sourceCfgs map[string]*config.SourceConfig) error {
 	// now, we simply check count repeatedly.
 	count := len(sourceCfgs)
 	ctx2, cancel2 := context.WithTimeout(context.Background(), waitWorkerV1Timeout)
@@ -291,7 +291,7 @@ func (s *Server) getSubtaskCfgsStagesV1Import(tctx *tcontext.Context) (
 }
 
 // addSourcesV1Import tries to add source config into the cluster for v1.0.x importing.
-func (s *Server) addSourcesV1Import(tctx *tcontext.Context, cfgs map[string]config.SourceConfig) error {
+func (s *Server) addSourcesV1Import(tctx *tcontext.Context, cfgs map[string]*config.SourceConfig) error {
 	var (
 		added []string
 		err   error
diff --git a/dm/master/bootstrap_test.go b/dm/master/bootstrap_test.go
index 258d9fe3f7..bec21ff9a3 100644
--- a/dm/master/bootstrap_test.go
+++ b/dm/master/bootstrap_test.go
@@ -94,8 +94,8 @@ func (t *testMaster) TestCollectSourceConfigFilesV1Import(c *C) {
 	cfgs, err = s.collectSourceConfigFilesV1Import(tctx)
 	c.Assert(err, IsNil)
 	c.Assert(cfgs, HasLen, 2)
-	c.Assert(cfgs[cfg1.SourceID], DeepEquals, *cfg1)
-	c.Assert(cfgs[cfg2.SourceID], DeepEquals, *cfg2)
+	c.Assert(cfgs[cfg1.SourceID], DeepEquals, cfg1)
+	c.Assert(cfgs[cfg2.SourceID], DeepEquals, cfg2)
 
 	// put a invalid source file.
 	c.Assert(ioutil.WriteFile(filepath.Join(s.cfg.V1SourcesPath, "invalid.yaml"), []byte("invalid-source-data"), 0o644), IsNil)
@@ -125,9 +125,9 @@ func (t *testMaster) TestWaitWorkersReadyV1Import(c *C) {
 	c.Assert(err, IsNil)
 	cfg2 := cfg1.Clone()
 	cfg2.SourceID = "mysql-replica-02"
-	cfgs := map[string]config.SourceConfig{
-		cfg1.SourceID: *cfg1,
-		cfg2.SourceID: *cfg2,
+	cfgs := map[string]*config.SourceConfig{
+		cfg1.SourceID: cfg1,
+		cfg2.SourceID: cfg2,
 	}
 
 	// no worker registered, timeout.
diff --git a/dm/master/server.go b/dm/master/server.go
index 08c4d673a3..548ced8eeb 100644
--- a/dm/master/server.go
+++ b/dm/master/server.go
@@ -1192,7 +1192,7 @@ func (s *Server) OperateSource(ctx context.Context, req *pb.OperateSourceRequest
 			err      error
 		)
 		for _, cfg := range cfgs {
-			err = s.scheduler.AddSourceCfg(*cfg)
+			err = s.scheduler.AddSourceCfg(cfg)
 			// return first error and try to revert, so user could copy-paste same start command after error
 			if err != nil {
 				resp.Msg = err.Error()
diff --git a/dm/master/server_test.go b/dm/master/server_test.go
index 85021c28ee..c3d47c8008 100644
--- a/dm/master/server_test.go
+++ b/dm/master/server_test.go
@@ -271,7 +271,7 @@ func testMockScheduler(ctx context.Context, wg *sync.WaitGroup, c *check.C, sour
 		cfg := config.NewSourceConfig()
 		cfg.SourceID = sources[i]
 		cfg.From.Password = password
-		c.Assert(scheduler2.AddSourceCfg(*cfg), check.IsNil, check.Commentf("all sources: %v", sources))
+		c.Assert(scheduler2.AddSourceCfg(cfg), check.IsNil, check.Commentf("all sources: %v", sources))
 		wg.Add(1)
 		ctx1, cancel1 := context.WithCancel(ctx)
 		cancels = append(cancels, cancel1)
@@ -303,7 +303,7 @@ func testMockSchedulerForRelay(ctx context.Context, wg *sync.WaitGroup, c *check
 		cfg := config.NewSourceConfig()
 		cfg.SourceID = sources[i]
 		cfg.From.Password = password
-		c.Assert(scheduler2.AddSourceCfg(*cfg), check.IsNil, check.Commentf("all sources: %v", sources))
+		c.Assert(scheduler2.AddSourceCfg(cfg), check.IsNil, check.Commentf("all sources: %v", sources))
 		wg.Add(1)
 		ctx1, cancel1 := context.WithCancel(ctx)
 		cancels = append(cancels, cancel1)
diff --git a/dm/worker/server.go b/dm/worker/server.go
index 3ceb65cbbc..3efd1fe58b 100644
--- a/dm/worker/server.go
+++ b/dm/worker/server.go
@@ -156,7 +156,7 @@ func (s *Server) Start() error {
 	}
 	if !bound.IsEmpty() {
 		log.L().Warn("worker has been assigned source before keepalive", zap.Stringer("bound", bound), zap.Bool("is deleted", bound.IsDeleted))
-		if err2 := s.enableHandleSubtasks(&sourceCfg, true); err2 != nil {
+		if err2 := s.enableHandleSubtasks(sourceCfg, true); err2 != nil {
 			return err2
 		}
 		log.L().Info("started to handle mysql source", zap.String("sourceCfg", sourceCfg.String()))
@@ -452,7 +452,7 @@ func (s *Server) observeSourceBound(ctx context.Context, rev int64) error {
 							}
 							log.L().Info("will recover observeSourceBound",
 								zap.String("relay source", cfg.SourceID))
-							return s.enableHandleSubtasks(&cfg, false)
+							return s.enableHandleSubtasks(cfg, false)
 						}()
 						if err2 != nil {
 							return err2
@@ -653,7 +653,7 @@ func (s *Server) operateSourceBound(bound ha.SourceBound) error {
 	if !ok {
 		return terror.ErrWorkerFailToGetSourceConfigFromEtcd.Generate(bound.Source)
 	}
-	return s.enableHandleSubtasks(&sourceCfg, true)
+	return s.enableHandleSubtasks(sourceCfg, true)
 }
 
 func (s *Server) enableHandleSubtasks(sourceCfg *config.SourceConfig, needLock bool) error {
@@ -704,7 +704,7 @@ func (s *Server) operateRelaySource(relaySource ha.RelaySource) error {
 	if !ok {
 		return terror.ErrWorkerFailToGetSourceConfigFromEtcd.Generate(relaySource.Source)
 	}
-	return s.enableRelay(&sourceCfg, true)
+	return s.enableRelay(sourceCfg, true)
 }
 
 func (s *Server) enableRelay(sourceCfg *config.SourceConfig, needLock bool) error {
diff --git a/pkg/ha/bound.go b/pkg/ha/bound.go
index 1d7eb67516..1aff76700b 100644
--- a/pkg/ha/bound.go
+++ b/pkg/ha/bound.go
@@ -185,11 +185,11 @@ func GetLastSourceBounds(cli *clientv3.Client) (map[string]SourceBound, int64, e
 // if source bound is empty, will return an empty sourceBound and an empty source config
 // if source bound is not empty but sourceConfig is empty, will return an error
 // if the source bound is different for over retryNum times, will return an error.
-func GetSourceBoundConfig(cli *clientv3.Client, worker string) (SourceBound, config.SourceConfig, int64, error) {
+func GetSourceBoundConfig(cli *clientv3.Client, worker string) (SourceBound, *config.SourceConfig, int64, error) {
 	var (
 		bound    SourceBound
 		newBound SourceBound
-		cfg      config.SourceConfig
+		cfg      *config.SourceConfig
 		ok       bool
 		retryNum = defaultGetSourceBoundConfigRetry
 	)
diff --git a/pkg/ha/bound_test.go b/pkg/ha/bound_test.go
index 9dd8f714d2..5a40b81e4d 100644
--- a/pkg/ha/bound_test.go
+++ b/pkg/ha/bound_test.go
@@ -125,10 +125,9 @@ func (t *testForEtcd) TestGetSourceBoundConfigEtcd(c *C) {
 	defer clearTestInfoOperation(c)
 
 	var (
-		worker   = "dm-worker-1"
-		source   = "mysql-replica-1"
-		bound    = NewSourceBound(source, worker)
-		emptyCfg config.SourceConfig
+		worker = "dm-worker-1"
+		source = "mysql-replica-1"
+		bound  = NewSourceBound(source, worker)
 	)
 	cfg, err := config.LoadFromFile(sourceSampleFile)
 	c.Assert(err, IsNil)
@@ -138,7 +137,7 @@ func (t *testForEtcd) TestGetSourceBoundConfigEtcd(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(rev1, Greater, int64(0))
 	c.Assert(bound1.IsEmpty(), IsTrue)
-	c.Assert(cfg1, DeepEquals, emptyCfg)
+	c.Assert(cfg1, IsNil)
 
 	rev2, err := PutSourceBound(etcdTestCli, bound)
 	c.Assert(err, IsNil)
diff --git a/pkg/ha/relay.go b/pkg/ha/relay.go
index b75268aa3a..9b041573a6 100644
--- a/pkg/ha/relay.go
+++ b/pkg/ha/relay.go
@@ -173,7 +173,7 @@ func GetRelayConfig(cli *clientv3.Client, worker string) (*config.SourceConfig,
 			return nil, 0, terror.ErrConfigMissingForBound.Generate(source)
 		}
 
-		return &cfg, rev2, nil
+		return cfg, rev2, nil
 	}
 	return nil, 0, terror.ErrWorkerRelayConfigChanging.Generate(worker, source, newSource)
 }
diff --git a/pkg/terror/error_list.go b/pkg/terror/error_list.go
index f214422a29..fb83de36a9 100644
--- a/pkg/terror/error_list.go
+++ b/pkg/terror/error_list.go
@@ -804,7 +804,7 @@ var (
 	ErrConfigEmptySourceID          = New(codeConfigEmptySourceID, ClassConfig, ScopeInternal, LevelMedium, "empty source-id not valid", "Please check the `source-id` config in configuration file.")
 	ErrConfigTooLongSourceID        = New(codeConfigTooLongSourceID, ClassConfig, ScopeInternal, LevelMedium, "too long source-id not valid", "Please check the `source-id` config in configuration file. The max source id length is 32.")
 	ErrConfigOnlineSchemeNotSupport = New(codeConfigOnlineSchemeNotSupport, ClassConfig, ScopeInternal, LevelMedium, "online scheme %s not supported", "Please check the `online-ddl-scheme` config in task configuration file. Only `ghost` and `pt` are currently supported.")
-	ErrConfigInvalidTimezone 		= New(codeConfigInvalidTimezone, ClassConfig, ScopeInternal, LevelMedium, "invalid timezone string: %s", "Please check the `timezone` config in task configuration file.")
+	ErrConfigInvalidTimezone        = New(codeConfigInvalidTimezone, ClassConfig, ScopeInternal, LevelMedium, "invalid timezone string: %s", "Please check the `timezone` config in task configuration file.")
 	ErrConfigParseFlagSet           = New(codeConfigParseFlagSet, ClassConfig, ScopeInternal, LevelMedium, "parse subtask config flag set", "")
 	ErrConfigDecryptDBPassword      = New(codeConfigDecryptDBPassword, ClassConfig, ScopeInternal, LevelMedium, "decrypt DB password %s failed", "")
 	ErrConfigMetaInvalid            = New(codeConfigMetaInvalid, ClassConfig, ScopeInternal, LevelMedium, "must specify `binlog-name` without GTID enabled for the source or specify `binlog-gtid` with GTID enabled for the source", "Please check the `meta` config in task configuration file.")
diff --git a/pkg/utils/common.go b/pkg/utils/common.go
index ef59108843..65ef2711f7 100644
--- a/pkg/utils/common.go
+++ b/pkg/utils/common.go
@@ -19,21 +19,16 @@ import (
 	"fmt"
 	"regexp"
 	"strings"
-	"time"
-
-	"github.com/pingcap/errors"
-
-	"github.com/pingcap/dm/pkg/log"
-	"github.com/pingcap/dm/pkg/terror"
 
 	"github.com/pingcap/failpoint"
 	tmysql "github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb-tools/pkg/dbutil"
 	"github.com/pingcap/tidb-tools/pkg/filter"
 	router "github.com/pingcap/tidb-tools/pkg/table-router"
-	"github.com/pingcap/tidb/types"
-	"github.com/pingcap/tidb/util/timeutil"
 	"go.uber.org/zap"
+
+	"github.com/pingcap/dm/pkg/log"
+	"github.com/pingcap/dm/pkg/terror"
 )
 
 // TrimCtrlChars returns a slice of the string s with all leading
@@ -214,40 +209,3 @@ func NonRepeatStringsEqual(a, b []string) bool {
 	}
 	return true
 }
-
-// ParseTimeZone parse location info from time offset("+08:00") or location string ("Asia/Shanghai")
-//
-// Copy from https://github.com/pingcap/tidb/blob/263a47e85ce04f74ec80d1d35b426618bc89b5a3/sessionctx/variable/varsutil.go#L411
-func ParseTimeZone(s string) (*time.Location, error) {
-	if strings.EqualFold(s, "SYSTEM") {
-		return timeutil.SystemLocation(), nil
-	}
-	loc, err := time.LoadLocation(s)
-	if err == nil {
-		return loc, nil
-	}
-	// The value can be given as a string indicating an offset from UTC, such as '+10:00' or '-6:00'.
-	// The time zone's value should in [-12:59,+14:00].
-	if strings.HasPrefix(s, "+") || strings.HasPrefix(s, "-") {
-		d, err := types.ParseDuration(nil, s[1:], 0)
-		if err == nil {
-			if s[0] == '-' {
-				if d.Duration > 12*time.Hour+59*time.Minute {
-					return nil, errors.Errorf("invalid time zone '%s'", s)
-				}
-			} else {
-				if d.Duration > 14*time.Hour {
-					return nil, errors.Errorf("invalid time zone '%s'", s)
-				}
-			}
-
-			ofst := int(d.Duration / time.Second)
-			if s[0] == '-' {
-				ofst = -ofst
-			}
-			return time.FixedZone("", ofst), nil
-		}
-	}
-
-	return nil, errors.Errorf("invalid time zone '%s'", s)
-}
diff --git a/pkg/utils/common_test.go b/pkg/utils/common_test.go
index c199c74df0..5b2b8de634 100644
--- a/pkg/utils/common_test.go
+++ b/pkg/utils/common_test.go
@@ -17,7 +17,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"time"
 
 	"github.com/DATA-DOG/go-sqlmock"
 	. "github.com/pingcap/check"
@@ -257,31 +256,3 @@ func (s *testCommonSuite) TestNonRepeatStringsEqual(c *C) {
 	c.Assert(NonRepeatStringsEqual([]string{}, []string{"1"}), IsFalse)
 	c.Assert(NonRepeatStringsEqual([]string{"1", "2"}, []string{"2", "3"}), IsFalse)
 }
-
-func (s *testCommonSuite) TestParseTimeZone(c *C) {
-	cases := map[string]time.Duration{
-		"+00:00":        time.Duration(0),
-		"+01:00":        time.Hour,
-		"-08:03":        -1 * (8*time.Hour + 3*time.Minute),
-		"-12:59":        -1 * (12*time.Hour + 59*time.Minute),
-		"+12:59":        12*time.Hour + 59*time.Minute,
-		"Asia/Shanghai": 8 * time.Hour,
-		"UTC":           time.Duration(0),
-	}
-	for k, v := range cases {
-		dur, err := ParseTimeZone(k)
-		c.Assert(err, IsNil)
-		c.Assert(dur, Equals, v)
-	}
-
-	badCases := []string{
-		"test",
-		"-13:00",
-		"+14:05",
-	}
-
-	for _, s := range badCases {
-		_, err := ParseTimeZone(s)
-		c.Assert(err, ErrorMatches, "invalid time zone.*")
-	}
-}