Hi Agustin, I'm unable to reproduce the same with PS 5.6.22 and 5.5.40 . Whenever I'm enable/disable slow log , it's not creating another slow log but add msg to the same file even if max_slowlog_size is 0 OR 8192. Is there anything specific in my.cnf which I need to mentioned? For PS 5.6.22, root@desktop:/var/lib/mysql# mysql -uroot -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 37 Server version: 5.6.22-71.0-log Percona Server (GPL), Release 71.0, Revision 726 Copyright (c) 2009-2014 Percona LLC and/or its affiliates Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> show variables like '%version%'; +-------------------------+--------------------------------------------------+ | Variable_name | Value | +-------------------------+--------------------------------------------------+ | innodb_version | 5.6.22-71.0 | | protocol_version | 10 | | slave_type_conversions | | | version | 5.6.22-71.0-log | | version_comment | Percona Server (GPL), Release 71.0, Revision 726 | | version_compile_machine | x86_64 | | version_compile_os | debian-linux-gnu | +-------------------------+--------------------------------------------------+ 7 rows in set (0.00 sec) mysql> show variables like 'max_slowlog_%'; +-------------------+-------+ | Variable_name | Value | +-------------------+-------+ | max_slowlog_files | 0 | | max_slowlog_size | 8192 | +-------------------+-------+ 2 rows in set (0.01 sec) mysql> show variables like 'slow_query_log%'; +------------------------------------+---------------------------------+ | Variable_name | Value | +------------------------------------+---------------------------------+ | slow_query_log | ON | | slow_query_log_always_write_time | 10.000000 | | slow_query_log_file | /var/lib/mysql/desktop-slow.log | | slow_query_log_timestamp_always | OFF | | slow_query_log_timestamp_precision | second | | slow_query_log_use_global_control | | +------------------------------------+---------------------------------+ 6 rows in set (0.00 sec) mysql> set global slow_query_log=0; Query OK, 0 rows affected (0.00 sec) mysql> set global slow_query_log=1; Query OK, 0 rows affected (0.00 sec) mysql> set global slow_query_log=0; Query OK, 0 rows affected (0.00 sec) mysql> set global slow_query_log=1; Query OK, 0 rows affected (0.00 sec) mysql> set global slow_query_log=0; Query OK, 0 rows affected (0.00 sec) mysql> show variables like 'slow_query_log%'; +------------------------------------+---------------------------------+ | Variable_name | Value | +------------------------------------+---------------------------------+ | slow_query_log | OFF | | slow_query_log_always_write_time | 10.000000 | | slow_query_log_file | /var/lib/mysql/desktop-slow.log | | slow_query_log_timestamp_always | OFF | | slow_query_log_timestamp_precision | second | | slow_query_log_use_global_control | | +------------------------------------+---------------------------------+ 6 rows in set (0.00 sec) mysql> set global slow_query_log=1; Query OK, 0 rows affected (0.00 sec) mysql> show variables like 'slow_query_log%'; +------------------------------------+---------------------------------+ | Variable_name | Value | +------------------------------------+---------------------------------+ | slow_query_log | ON | | slow_query_log_always_write_time | 10.000000 | | slow_query_log_file | /var/lib/mysql/desktop-slow.log | | slow_query_log_timestamp_always | OFF | | slow_query_log_timestamp_precision | second | | slow_query_log_use_global_control | | +------------------------------------+---------------------------------+ 6 rows in set (0.00 sec) mysql> root@desktop:/var/lib/mysql# ll total 307456 drwx------ 6 mysql mysql 4096 Feb 3 11:16 ./ drwxr-xr-x 72 root root 4096 Feb 1 20:09 ../ -rw-rw---- 1 mysql mysql 56 Jan 16 14:59 auto.cnf -rw-r--r-- 1 root root 0 Jan 16 14:59 debian-5.6.flag -rw-r----- 1 mysql root 82017 Jan 27 13:29 desktop.err -rw-rw---- 1 mysql mysql 5 Feb 3 11:15 desktop.pid -rw-rw---- 1 mysql mysql 630 Feb 3 11:21 desktop-slow.log -rw-r----- 1 mysql root 125773 Feb 3 11:15 error.log -rw-rw---- 1 mysql mysql 213909504 Feb 3 11:15 ibdata1 -rw-rw---- 1 mysql mysql 50331648 Feb 3 11:15 ib_logfile0 -rw-rw---- 1 mysql mysql 50331648 Feb 3 11:15 ib_logfile1 drwx------ 2 mysql mysql 4096 Jan 16 14:59 mysql/ -rw------- 1 root root 11 Jan 16 14:59 mysql_upgrade_info dr-x------ 2 mysql mysql 4096 Jan 27 13:30 nil/ drwx------ 2 mysql mysql 4096 Jan 16 14:59 performance_schema/ drwx------ 2 mysql mysql 4096 Jan 16 14:59 test/ root@desktop:/var/lib/mysql# root@desktop:/var/lib/mysql# cat desktop-slow.log /usr/sbin/mysqld, Version: 5.6.22-71.0-log (Percona Server (GPL), Release 71.0, Revision 726). started with: Tcp port: 3306 Unix socket: /var/run/mysqld/mysqld.sock Time Id Command Argument /usr/sbin/mysqld, Version: 5.6.22-71.0-log (Percona Server (GPL), Release 71.0, Revision 726). started with: Tcp port: 3306 Unix socket: /var/run/mysqld/mysqld.sock Time Id Command Argument /usr/sbin/mysqld, Version: 5.6.22-71.0-log (Percona Server (GPL), Release 71.0, Revision 726). started with: Tcp port: 3306 Unix socket: /var/run/mysqld/mysqld.sock Time Id Command Argument root@desktop:/var/lib/mysql# ===========================With 5.5.40 ========================= nilnandan@desktop:~/sandboxes/msb_5_5_40$ mysql -uroot -p --socket=/tmp/mysql_sandbox5540.sock Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 2 Server version: 5.5.40-36.1-log Percona Server (GPL), Release 36.1, Revision 707 Copyright (c) 2009-2014 Percona LLC and/or its affiliates Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> show variables like '%version%'; +-------------------------+--------------------------------------------------+ | Variable_name | Value | +-------------------------+--------------------------------------------------+ | innodb_version | 5.5.40-36.1 | | protocol_version | 10 | | slave_type_conversions | | | version | 5.5.40-36.1-log | | version_comment | Percona Server (GPL), Release 36.1, Revision 707 | | version_compile_machine | x86_64 | | version_compile_os | Linux | +-------------------------+--------------------------------------------------+ 7 rows in set (0.01 sec) mysql> show variables like 'max_slowlog_%'; +-------------------+-------+ | Variable_name | Value | +-------------------+-------+ | max_slowlog_files | 0 | | max_slowlog_size | 0 | +-------------------+-------+ 2 rows in set (0.00 sec) mysql> show variables like 'slow_query_log%'; +------------------------------------+-------------------------------------------------------------+ | Variable_name | Value | +------------------------------------+-------------------------------------------------------------+ | slow_query_log | ON | | slow_query_log_always_write_time | 10.000000 | | slow_query_log_file | /home/nilnandan/sandboxes/msb_5_5_40/data/msandbox-slow.log | | slow_query_log_timestamp_always | OFF | | slow_query_log_timestamp_precision | second | | slow_query_log_use_global_control | | +------------------------------------+-------------------------------------------------------------+ 6 rows in set (0.00 sec) mysql> set global slow_query_log=0; Query OK, 0 rows affected (0.00 sec) mysql> show variables like 'slow_query_log%'; +------------------------------------+-------------------------------------------------------------+ | Variable_name | Value | +------------------------------------+-------------------------------------------------------------+ | slow_query_log | OFF | | slow_query_log_always_write_time | 10.000000 | | slow_query_log_file | /home/nilnandan/sandboxes/msb_5_5_40/data/msandbox-slow.log | | slow_query_log_timestamp_always | OFF | | slow_query_log_timestamp_precision | second | | slow_query_log_use_global_control | | +------------------------------------+-------------------------------------------------------------+ 6 rows in set (0.00 sec) mysql> set global slow_query_log=1; Query OK, 0 rows affected (0.00 sec) mysql> show variables like 'slow_query_log%'; +------------------------------------+-------------------------------------------------------------+ | Variable_name | Value | +------------------------------------+-------------------------------------------------------------+ | slow_query_log | ON | | slow_query_log_always_write_time | 10.000000 | | slow_query_log_file | /home/nilnandan/sandboxes/msb_5_5_40/data/msandbox-slow.log | | slow_query_log_timestamp_always | OFF | | slow_query_log_timestamp_precision | second | | slow_query_log_use_global_control | | +------------------------------------+-------------------------------------------------------------+ 6 rows in set (0.00 sec) mysql> quit Bye nilnandan@desktop:~/sandboxes/msb_5_5_40$ cd data/ nilnandan@desktop:~/sandboxes/msb_5_5_40/data$ ll total 36960 drwx------ 5 nilnandan nilnandan 4096 Feb 3 11:26 ./ drwxrwxr-x 4 nilnandan nilnandan 4096 Feb 3 11:26 ../ -rw-rw---- 1 nilnandan nilnandan 27262976 Jan 22 16:23 ibdata1 -rw-rw---- 1 nilnandan nilnandan 5242880 Feb 3 11:26 ib_logfile0 -rw-rw---- 1 nilnandan nilnandan 5242880 Feb 3 11:26 ib_logfile1 -rw-r----- 1 nilnandan nilnandan 6210 Feb 3 11:26 msandbox.err -rw-rw---- 1 nilnandan nilnandan 494 Feb 3 11:27 msandbox-slow.log drwx------ 2 nilnandan nilnandan 16384 Jan 6 15:54 mysql/ -rw-rw---- 1 nilnandan nilnandan 5 Feb 3 11:26 mysql_sandbox5540.pid drwx------ 2 nilnandan nilnandan 4096 Jan 6 15:54 performance_schema/ drwx------ 2 nilnandan nilnandan 4096 Jan 22 11:45 test/ nilnandan@desktop:~/sandboxes/msb_5_5_40/data$ vim msandbox-slow.log nilnandan@desktop:~/sandboxes/msb_5_5_40/data$ cat msandbox-slow.log /home/nilnandan/Downloads/Softwares/5.5.40/bin/mysqld, Version: 5.5.40-36.1-log (Percona Server (GPL), Release 36.1, Revision 707). started with: Tcp port: 5540 Unix socket: /tmp/mysql_sandbox5540.sock Time Id Command Argument /home/nilnandan/Downloads/Softwares/5.5.40/bin/mysqld, Version: 5.5.40-36.1-log (Percona Server (GPL), Release 36.1, Revision 707). started with: Tcp port: 5540 Unix socket: /tmp/mysql_sandbox5540.sock Time Id Command Argument nilnandan@desktop:~/sandboxes/msb_5_5_40/data$