diff --git a/mdbx.h b/mdbx.h
index d8453d05..421d833b 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -327,7 +327,7 @@ typedef int(MDBX_cmp_func)(const MDBX_val *a, const MDBX_val *b);
 /* Store multiple data items in one call. Only for MDBX_DUPFIXED. */
 #define MDBX_MULTIPLE 0x80000u
 
-/* Transaction Flags*/
+/* Transaction Flags */
 /* Do not block when starting a write transaction */
 #define MDBX_TRYTXN 0x10000000u
 
diff --git a/src/bits.h b/src/bits.h
index b22c1f25..7fe6836c 100644
--- a/src/bits.h
+++ b/src/bits.h
@@ -553,8 +553,8 @@ struct MDBX_txn {
 
 /* Transaction Flags */
 /* mdbx_txn_begin() flags */
-#define MDBX_TXN_BEGIN_FLAGS_PERSISTENT (MDBX_NOMETASYNC | MDBX_NOSYNC | MDBX_RDONLY)
-#define MDBX_TXN_BEGIN_FLAGS (MDBX_TXN_BEGIN_FLAGS_PERSISTENT | MDBX_TRYTXN)
+#define MDBX_TXN_BEGIN_FLAGS                                                   \
+  (MDBX_NOMETASYNC | MDBX_NOSYNC | MDBX_RDONLY | MDBX_TRYTXN)
 #define MDBX_TXN_NOMETASYNC                                                    \
   MDBX_NOMETASYNC                   /* don't sync meta for this txn on commit */
 #define MDBX_TXN_NOSYNC MDBX_NOSYNC /* don't sync this txn on commit */
diff --git a/src/lck-posix.c b/src/lck-posix.c
index 0c8cb41b..14ce3d50 100644
--- a/src/lck-posix.c
+++ b/src/lck-posix.c
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2015-2017 Leonid Yuriev <leo@yuriev.ru>
  * and other libmdbx authors: please see AUTHORS file.
  * All rights reserved.
@@ -186,9 +186,9 @@ static int mdbx_robust_lock(MDBX_env *env, pthread_mutex_t *mutex) {
 
 static int mdbx_robust_trylock(MDBX_env *env, pthread_mutex_t *mutex) {
   int rc = pthread_mutex_trylock(mutex);
-  if (unlikely(rc != 0))
+  if (unlikely(rc != 0 && rc != EBUSY))
     rc = mdbx_mutex_failed(env, mutex, rc);
-  return rc;
+  return (rc != EBUSY) ? rc : MDBX_BUSY;
 }
 
 static int mdbx_robust_unlock(MDBX_env *env, pthread_mutex_t *mutex) {
@@ -213,16 +213,10 @@ void mdbx_rdt_unlock(MDBX_env *env) {
     mdbx_panic("%s() failed: errcode %d\n", mdbx_func_, rc);
 }
 
-int mdbx_txn_lock(MDBX_env *env) {
+int mdbx_txn_lock(MDBX_env *env, bool dontwait) {
   mdbx_trace(">>");
-  int rc = mdbx_robust_lock(env, &env->me_lck->mti_wmutex);
-  mdbx_trace("<< rc %d", rc);
-  return MDBX_IS_ERROR(rc) ? rc : MDBX_SUCCESS;
-}
-
-int mdbx_txn_trylock(MDBX_env *env) {
-  mdbx_trace(">>");
-  int rc = mdbx_robust_trylock(env, &env->me_lck->mti_wmutex);
+  int rc = dontwait ? mdbx_robust_trylock(env, &env->me_lck->mti_wmutex)
+                    : mdbx_robust_lock(env, &env->me_lck->mti_wmutex);
   mdbx_trace("<< rc %d", rc);
   return MDBX_IS_ERROR(rc) ? rc : MDBX_SUCCESS;
 }
@@ -327,9 +321,7 @@ static int __cold mdbx_mutex_failed(MDBX_env *env, pthread_mutex_t *mutex,
 #endif /* MDBX_USE_ROBUST */
 
   mdbx_error("mutex (un)lock failed, %s", mdbx_strerror(rc));
-  if (rc == EBUSY) {
-    rc = MDBX_BUSY;
-  } else if (rc != EDEADLK && rc != EBUSY) {
+  if (rc != EDEADLK) {
     env->me_flags |= MDBX_FATAL_ERROR;
     rc = MDBX_PANIC;
   }
diff --git a/src/lck-windows.c b/src/lck-windows.c
index d3340d58..672512a7 100644
--- a/src/lck-windows.c
+++ b/src/lck-windows.c
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2015-2017 Leonid Yuriev <leo@yuriev.ru>
  * and other libmdbx authors: please see AUTHORS file.
  * All rights reserved.
@@ -126,20 +126,13 @@ static __inline BOOL funlock(mdbx_filehandle_t fd, uint64_t offset,
 #define LCK_BODY LCK_BODY_OFFSET, LCK_BODY_LEN
 #define LCK_WHOLE 0, LCK_MAXLEN
 
-int mdbx_txn_lock(MDBX_env *env) {
-  if (flock(env->me_fd, LCK_EXCLUSIVE | LCK_WAITFOR, LCK_BODY))
-    return MDBX_SUCCESS;
-  return GetLastError();
-}
-
-int mdbx_txn_trylock(MDBX_env *env) {
-  if (flock(env->me_fd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_BODY))
+int mdbx_txn_lock(MDBX_env *env, bool dontwait) {
+  if (flock(env->me_fd, dontwait ? (LCK_EXCLUSIVE | LCK_DONTWAIT)
+                                 : (LCK_EXCLUSIVE | LCK_WAITFOR),
+            LCK_BODY))
     return MDBX_SUCCESS;
   int rc = GetLastError();
-  if (rc == ERROR_LOCK_VIOLATION) {
-    rc = MDBX_BUSY;
-  }
-  return rc;
+  return (!dontwait || rc != ERROR_LOCK_VIOLATION) ? rc : MDBX_BUSY;
 }
 
 void mdbx_txn_unlock(MDBX_env *env) {
diff --git a/src/mdbx.c b/src/mdbx.c
index 01373842..57b74336 100644
--- a/src/mdbx.c
+++ b/src/mdbx.c
@@ -2313,7 +2313,7 @@ int mdbx_env_sync(MDBX_env *env, int force) {
       (!env->me_txn0 || env->me_txn0->mt_owner != mdbx_thread_self());
 
   if (outside_txn) {
-    int rc = mdbx_txn_lock(env);
+    int rc = mdbx_txn_lock(env, false);
     if (unlikely(rc != MDBX_SUCCESS))
       return rc;
   }
@@ -2342,7 +2342,7 @@ int mdbx_env_sync(MDBX_env *env, int force) {
       if (unlikely(rc != MDBX_SUCCESS))
         return rc;
 
-      rc = mdbx_txn_lock(env);
+      rc = mdbx_txn_lock(env, false);
       if (unlikely(rc != MDBX_SUCCESS))
         return rc;
 
@@ -2587,7 +2587,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
   } else {
     /* Not yet touching txn == env->me_txn0, it may be active */
     mdbx_jitter4testing(false);
-    rc = F_ISSET(flags, MDBX_TRYTXN) ? mdbx_txn_trylock(env) : mdbx_txn_lock(env);
+    rc = mdbx_txn_lock(env, F_ISSET(flags, MDBX_TRYTXN));
     if (unlikely(rc))
       return rc;
 
@@ -2689,7 +2689,6 @@ int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags,
                    MDBX_txn **ret) {
   MDBX_txn *txn;
   MDBX_ntxn *ntxn;
-  //unsigned pflags;
   int rc, size, tsize;
 
   if (unlikely(!env || !ret))
@@ -2744,7 +2743,7 @@ int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags,
   txn->mt_dbxs = env->me_dbxs; /* static */
   txn->mt_dbs = (MDBX_db *)((char *)txn + tsize);
   txn->mt_dbflags = (uint8_t *)txn + size - env->me_maxdbs;
-  txn->mt_flags = flags & MDBX_TXN_BEGIN_FLAGS_PERSISTENT;
+  txn->mt_flags = flags;
   txn->mt_env = env;
 
   if (parent) {
@@ -4468,7 +4467,7 @@ LIBMDBX_API int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower,
       return MDBX_EACCESS;
 
     if (outside_txn) {
-      int err = mdbx_txn_lock(env);
+      int err = mdbx_txn_lock(env, false);
       if (unlikely(err != MDBX_SUCCESS))
         return err;
     }
@@ -9796,7 +9795,7 @@ static int __cold mdbx_env_copy_asis(MDBX_env *env, mdbx_filehandle_t fd) {
     goto bailout; /* FIXME: or just return? */
 
   /* Temporarily block writers until we snapshot the meta pages */
-  rc = mdbx_txn_lock(env);
+  rc = mdbx_txn_lock(env, false);
   if (unlikely(rc != MDBX_SUCCESS))
     goto bailout;
 
@@ -9881,7 +9880,7 @@ int __cold mdbx_env_set_flags(MDBX_env *env, unsigned flags, int onoff) {
   if (unlikely(flags & ~CHANGEABLE))
     return MDBX_EINVAL;
 
-  int rc = mdbx_txn_lock(env);
+  int rc = mdbx_txn_lock(env, false);
   if (unlikely(rc))
     return rc;
 
diff --git a/src/osal.h b/src/osal.h
index ad9fd275..871e52b0 100644
--- a/src/osal.h
+++ b/src/osal.h
@@ -505,8 +505,7 @@ void mdbx_lck_destroy(MDBX_env *env);
 int mdbx_rdt_lock(MDBX_env *env);
 void mdbx_rdt_unlock(MDBX_env *env);
 
-int mdbx_txn_lock(MDBX_env *env);
-int mdbx_txn_trylock(MDBX_env *env);
+int mdbx_txn_lock(MDBX_env *env, bool dontwait);
 void mdbx_txn_unlock(MDBX_env *env);
 
 int mdbx_rpid_set(MDBX_env *env);
diff --git a/test/config.h b/test/config.h
index aecfcd3e..c2ac1389 100644
--- a/test/config.h
+++ b/test/config.h
@@ -20,7 +20,14 @@
 
 #define ACTOR_ID_MAX INT16_MAX
 
-enum actor_testcase { ac_none, ac_hill, ac_deadread, ac_deadwrite, ac_jitter, ac_try };
+enum actor_testcase {
+  ac_none,
+  ac_hill,
+  ac_deadread,
+  ac_deadwrite,
+  ac_jitter,
+  ac_try
+};
 
 enum actor_status {
   as_unknown,
diff --git a/test/dead.cc b/test/dead.cc
index acea1193..c7b338ff 100644
--- a/test/dead.cc
+++ b/test/dead.cc
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2017 Leonid Yuriev <leo@yuriev.ru>
  * and other libmdbx authors: please see AUTHORS file.
  * All rights reserved.
@@ -25,7 +25,7 @@ bool testcase_deadread::setup() {
 
 bool testcase_deadread::run() {
   db_open();
-  txn_begin(MDBX_RDONLY);
+  txn_begin(true);
   return true;
 }
 
@@ -50,7 +50,7 @@ bool testcase_deadwrite::setup() {
 
 bool testcase_deadwrite::run() {
   db_open();
-  txn_begin(0);
+  txn_begin(false);
   return true;
 }
 
diff --git a/test/hill.cc b/test/hill.cc
index 2b7aeb00..72a6e95b 100644
--- a/test/hill.cc
+++ b/test/hill.cc
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2017 Leonid Yuriev <leo@yuriev.ru>
  * and other libmdbx authors: please see AUTHORS file.
  * All rights reserved.
@@ -28,7 +28,7 @@ bool testcase_hill::setup() {
 bool testcase_hill::run() {
   db_open();
 
-  txn_begin(0);
+  txn_begin(false);
   MDBX_dbi dbi = db_table_open(true);
   txn_end(false);
 
@@ -70,7 +70,7 @@ bool testcase_hill::run() {
   uint64_t serial_count = 0;
   unsigned txn_nops = 0;
   if (!txn_guard)
-    txn_begin(0);
+    txn_begin(false);
 
   while (should_continue()) {
     const keygen::serial_t a_serial = serial_count;
@@ -91,7 +91,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_put(insert-a.1)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -104,7 +104,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_put(insert-b)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -118,7 +118,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_put(update-a: 1->0)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -129,7 +129,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_del(b)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -164,7 +164,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_put(update-a: 0->1)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -177,7 +177,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_put(insert-b)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -189,7 +189,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_del(a)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -200,7 +200,7 @@ bool testcase_hill::run() {
       failure_perror("mdbx_del(b)", rc);
 
     if (++txn_nops >= config.params.batch_write) {
-      txn_restart(false, 0);
+      txn_restart(false, false);
       txn_nops = 0;
     }
 
@@ -212,7 +212,7 @@ bool testcase_hill::run() {
 
   if (dbi) {
     if (config.params.drop_table && !mode_readonly()) {
-      txn_begin(0);
+      txn_begin(false);
       db_table_drop(dbi);
       txn_end(false);
     } else
diff --git a/test/jitter.cc b/test/jitter.cc
index 27f208a3..92d272e1 100644
--- a/test/jitter.cc
+++ b/test/jitter.cc
@@ -30,7 +30,7 @@ bool testcase_jitter::run() {
 
     if (flipcoin()) {
       jitter_delay();
-      txn_begin(MDBX_RDONLY);
+      txn_begin(true);
       fetch_canary();
       jitter_delay();
       txn_end(flipcoin());
@@ -51,7 +51,7 @@ bool testcase_jitter::run() {
 
     if (flipcoin()) {
       jitter_delay();
-      txn_begin(MDBX_RDONLY);
+      txn_begin(true);
       jitter_delay();
       txn_end(flipcoin());
     }
diff --git a/test/test.cc b/test/test.cc
index 6bb17735..f1dc2264 100644
--- a/test/test.cc
+++ b/test/test.cc
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2017 Leonid Yuriev <leo@yuriev.ru>
  * and other libmdbx authors: please see AUTHORS file.
  * All rights reserved.
@@ -177,18 +177,21 @@ void testcase::db_close() {
   log_trace("<< db_close");
 }
 
-void testcase::txn_begin(unsigned flags) {
-  log_trace(">> txn_begin(%s)", flags & MDBX_RDONLY ? "read-only" : "read-write");
+void testcase::txn_begin(bool readonly, unsigned flags) {
+  assert((flags & MDBX_RDONLY) == 0);
+  log_trace(">> txn_begin(%s, 0x%04X)", readonly ? "read-only" : "read-write",
+            flags);
   assert(!txn_guard);
 
   MDBX_txn *txn = nullptr;
-  int rc =
-      mdbx_txn_begin(db_guard.get(), nullptr, flags, &txn);
+  int rc = mdbx_txn_begin(db_guard.get(), nullptr,
+                          readonly ? flags | MDBX_RDONLY : flags, &txn);
   if (unlikely(rc != MDBX_SUCCESS))
     failure_perror("mdbx_txn_begin()", rc);
   txn_guard.reset(txn);
 
-  log_trace("<< txn_begin(%s)", flags & MDBX_RDONLY ? "read-only" : "read-write");
+  log_trace("<< txn_begin(%s, 0x%04X)", readonly ? "read-only" : "read-write",
+            flags);
 }
 
 void testcase::txn_end(bool abort) {
@@ -209,10 +212,10 @@ void testcase::txn_end(bool abort) {
   log_trace("<< txn_end(%s)", abort ? "abort" : "commit");
 }
 
-void testcase::txn_restart(bool abort, unsigned flags) {
+void testcase::txn_restart(bool abort, bool readonly, unsigned flags) {
   if (txn_guard)
     txn_end(abort);
-  txn_begin(flags);
+  txn_begin(readonly, flags);
 }
 
 bool testcase::wait4start() {
diff --git a/test/test.h b/test/test.h
index 500caef0..67fadebf 100644
--- a/test/test.h
+++ b/test/test.h
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2017 Leonid Yuriev <leo@yuriev.ru>
  * and other libmdbx authors: please see AUTHORS file.
  * All rights reserved.
@@ -104,9 +104,9 @@ protected:
   void db_prepare();
   void db_open();
   void db_close();
-  void txn_begin(unsigned flags);
+  void txn_begin(bool readonly, unsigned flags = 0);
   void txn_end(bool abort);
-  void txn_restart(bool abort, unsigned flags);
+  void txn_restart(bool abort, bool readonly, unsigned flags = 0);
   void fetch_canary();
   void update_canary(uint64_t increment);
   void kick_progress(bool active) const;
@@ -130,8 +130,8 @@ protected:
     generate_pair(serial, key, data, data_age);
   }
 
-  unsigned mode_readonly() const {
-    return (config.params.mode_flags & MDBX_RDONLY) ? MDBX_RDONLY : 0;
+  bool mode_readonly() const {
+    return (config.params.mode_flags & MDBX_RDONLY) ? true : false;
   }
 
 public:
diff --git a/test/try.cc b/test/try.cc
index 4071c24c..1deae71d 100644
--- a/test/try.cc
+++ b/test/try.cc
@@ -15,8 +15,7 @@ bool testcase_try::run() {
 
   MDBX_txn *txn = nullptr;
   MDBX_txn *txn2 = nullptr;
-  int rc =
-      mdbx_txn_begin(db_guard.get(), nullptr, 0, &txn);
+  int rc = mdbx_txn_begin(db_guard.get(), nullptr, 0, &txn);
   if (unlikely(rc != MDBX_SUCCESS))
     failure_perror("mdbx_txn_begin(MDBX_TRYTXN)", rc);
   else {