diff --git a/tests/bugs/gh_6947_test.py b/tests/bugs/gh_6947_test.py
new file mode 100644
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+++ b/tests/bugs/gh_6947_test.py
@@ -0,0 +1,151 @@
+#coding:utf-8
+
+"""
+ID:          issue-6947
+ISSUE:       6947
+TITLE:       Query to mon$ tables does not return data when the encryption/decryption thread is running
+DESCRIPTION:
+  Test creates table with wide indexed column and add some data to it.
+  Volume of data must be big enough so that the encryption thread will not complete instantly.
+
+  Then 'ALTER DATABASE ENCRYPT...' is issued and we start loop 'select mon$crypt_page from mon$database'.
+  This loop must return NOT LESS than <MIN_DISTINCT_ENCRYPTED_PAGES> values greater than zero (i.e. it must
+  show progress of this process; zero values mean that encryption either did not start or already finished).
+  On each iteration we also check whether encryption completed (use ISQL call with 'show database' command)
+  or may be it is too slow and we have to cancel loop because of expiration <max_encrypt_decrypt_ms> limit.
+
+  When this loop is finished, we check number of elements in the encrypted_pages_set (unique values returned
+  by query from mon$database) and show outcome message.
+
+  Confirmed bug on 5.0.0.219 (Windows), 5.0.0.236 (Linux).
+  Checked on 5.0.0.240 (Windows; SS/Cs), 5.0.0.241 (Linux; SS/CS).
+FBTEST:      bugs.core_6947
+NOTES:
+    [20.06.2022] pzotov
+    Settings for encryption are taken from act.files_dir/'test_config.ini' file.
+    Checked on 5.0.0.509 - both Windows and Linux.
+"""
+
+import datetime as py_dt
+from datetime import timedelta
+import time
+
+import pytest
+from firebird.qa import *
+from firebird.driver import ShutdownMode, ShutdownMethod, DatabaseError
+
+FLD_LEN = 500
+N_ROWS = 50000
+MIN_DISTINCT_ENCRYPTED_PAGES = 3
+
+init_ddl = f"""
+    recreate table test(s varchar({FLD_LEN}));
+    commit;
+    set term ^;
+    execute block as
+        declare n int = {N_ROWS};
+    begin
+        while (n>0) do
+        begin
+            insert into test(s) values(lpad('', {FLD_LEN}, uuid_to_char(gen_uuid())));
+            n = n - 1;
+        end
+    end
+    ^
+    -- for debug, trace must be started with log_proc = true:
+    create procedure sp_tmp(a_page int) as
+    begin
+        -- nop --
+    end
+    ^
+    set term ;^
+    commit;
+    create index test_s on test(s);
+"""
+db = db_factory(init = init_ddl)
+act = python_act('db', substitutions=[('[ \t]+', ' ')])
+
+expected_stdout = f"Expected: query to mon$database returned not less then {MIN_DISTINCT_ENCRYPTED_PAGES} encrypted pages."
+
+@pytest.mark.encryption
+@pytest.mark.version('>=5.0')
+def test_1(act: Action, capsys):
+
+    act.db.set_sync_write() # here we want DB be  encrypted for some *valuable* time
+
+    # QA_GLOBALS -- dict, is defined in qa/plugin.py, obtain settings
+    # from act.files_dir/'test_config.ini':
+    enc_settings = QA_GLOBALS['encryption']
+
+    max_encrypt_decrypt_ms = int(enc_settings['max_encrypt_decrypt_ms']) # 5000
+    encryption_plugin = enc_settings['encryption_plugin'] # fbSampleDbCrypt
+    encryption_holder  = enc_settings['encryption_holder'] # fbSampleKeyHolder
+    encryption_key = enc_settings['encryption_key'] # Red
+
+    encryption_started = False
+    encryption_finished = False
+    encrypted_pages_set = set()
+
+    with act.db.connect() as con:
+
+        t1=py_dt.datetime.now()
+        sttm = f'alter database encrypt with "{encryption_plugin}" key "{encryption_key}"'
+        try:
+            con.execute_immediate(sttm)
+            con.commit()
+            encryption_started = True
+        except DatabaseError as e:
+            # -ALTER DATABASE failed
+            # -Crypt plugin fbSampleDbCrypt failed to load
+            #  ==> no sense to do anything else, encryption_started remains False.
+            print( e.__str__() )
+
+
+        cur = con.cursor()
+        cu2 = con.cursor()
+
+        ps = cur.prepare('select mon$crypt_page from mon$database')
+
+        while encryption_started:
+            t2=py_dt.datetime.now()
+            d1=t2-t1
+            if d1.seconds*1000 + d1.microseconds//1000 > max_encrypt_decrypt_ms:
+                print(f'TIMEOUT EXPIRATION: encryption took {d1.seconds*1000 + d1.microseconds//1000} ms which exceeds limit = {max_encrypt_decrypt_ms} ms.')
+                break
+
+            cur.execute(ps)
+            p = cur.fetchone()[0]
+            cu2.callproc('sp_tmp', [ p, ] )
+            con.commit()
+
+            if p > 0:
+                encrypted_pages_set.add(p)
+                if len(encrypted_pages_set) >= MIN_DISTINCT_ENCRYPTED_PAGES:
+                    # We got enough data from mon$database to conclude that encryption is in PROGRESS.
+                    break
+
+            # Possible output:
+            #     Database not encrypted
+            #     Database encrypted, crypt thread not complete
+            act.isql(switches=['-q'], input = 'show database;', combine_output = True)
+            if 'Database encrypted' in act.stdout:
+                if 'not complete' in act.stdout:
+                    pass
+                else:
+                    encryption_finished = True
+                    break
+            act.reset()
+
+    if encryption_started:
+        if len(encrypted_pages_set) >= MIN_DISTINCT_ENCRYPTED_PAGES:
+            print(expected_stdout)
+        elif len(encrypted_pages_set) > 0:
+            print(f'PROBABLY ERROR OR TOO SLOW ENCRYPTION: found {len(encrypted_pages_set)} encrypted pages, minimal expected: {MIN_DISTINCT_ENCRYPTED_PAGES}')
+        else:
+            print(f'ERROR: query to mon$database was blocked during encryption.')
+    else:
+        print('ERROR: nothing was tested because encryption did not start.')
+
+    act.expected_stdout = expected_stdout
+    act.stdout = capsys.readouterr().out
+    assert act.clean_stdout == act.clean_expected_stdout