MonetDB Server Applications

MonetDB Server Applications giulia Mon, 02/24/2020 - 15:17

Note: on MS Windows the server programs monetdb and monetdbd are not available. Only mserver5 is available to start a MonetDB server. See installed batch files: M5server.bat and MSQLserver.bat (which calls M5server.bat).


monetdb sjoerd Tue, 04/26/2011 - 12:33


monetdb − control a MonetDB Database Server instance


monetdb [ monetdb_options ] command [ command_options ] [ command_args ]


Monetdb allows an administrator of the MonetDB Database Server to perform various operations on the databases in the server. It relies on monetdbd(1) running in the background for all operations.


Monetdb_options affect all commands and control the general behavior of monetdb.


Suppresses all standard progress messages, only writing output to stderr if an error occurred.

−h hostname

Connect to hostname instead of attempting a connection over the local UNIX socket. This allows monetdb to connect to a remote monetdbd(1). The use of this option requires −P (see below). If hostname starts with a forward slash (/), hostname is assumed to be the directory where the UNIX sockets are stored. In that case, the −P option is not allowed.

−p port

Connects to the given portnumber instead of the default (50000). Requires −h to be given as option too.

−P passphrase

Specifies the passphrase necessary to login to a remote monetdbd(1). This option requires −h to be given as well. A bad passphrase causes monetdb to fail to login, and hence fail to perform any remote action.


Show version, equal to monetdb version.


The commands for the monetdb utility are create, destroy, lock, release, status, start, stop, kill, profilerstart, profilerstop, snapshot, set, get, inherit, discover, help, and version. The commands facilitate adding, removing, maintaining, starting and stopping a database inside the MonetDB Database Server.

For all commands, database arguments can be glob-like expressions. This allows to do wildcard matches. For details on the syntax, see EXPRESSIONS.
[−m pattern] [−p password] database [database ...]

Initializes a new database in the MonetDB Database Server. A database created with this command makes it available under its database name, but not yet for use by clients, as the database is put into maintenance mode. This allows the database administrator to perform initialization steps before releasing it to users, unless the −p argument is supplied. See also monetdb lock. The name of the database must match the expression [A−Za−z0−9−_]+.

With the −m flag, instead of creating a database, a multiplex-funnel is created. See section MULTIPLEX-FUNNEL in monetdbd(1). The pattern argument is not fully the same as a pattern for connecting or discovery. Each parallel target for the multiplex-funnel is given as username+password@pattern sequence, separated by commas. Here the pattern is an ordinary pattern as would be used for connecting to a database, and can hence also be just the name of a database.

−p password

The −p flag allows to create a database with the given password for the monetdb user. Since this protects the database from being accessed via well-known credentials, the created database is not locked after creation. This way, a new database can be created and used right away using the password supplied.

destroy [−f] database [database ...]

Removes the given database, including all its data and logfiles. Once destroy has completed, all data is lost. Be careful when using this command.


By default, a confirmation question is asked, however the −f option, when provided, suppresses this question and removal is executed right away. Note that without this option you cannot destroy a running database, bring it down first using the stop command.

lock database [database ...]

Puts the given database in maintenance mode. A database under maintenance can only be connected to by an administrator account (by default the monetdb account). A database which is under maintenance is not started automatically by monetdbd(1), the MonetDB Database Server, when clients request for it. Use the release command to bring the database back for normal usage. To start a database which is under maintenance for administrator access, the start command can be used.

release database [database ...]

Brings back a database from maintenance mode. A released database is available again for normal use by any client, and is started on demand. Use the lock command to take a database under maintenance.

status [−lc] [−s states] [database ...]

Shows the state of the given database, or, when none given, all known databases. Three modes control the level of detail in the displayed output. By default a condensed one-line output per database format is used. This output resembles pretty much the output of various xxxstat programs, and is ideal for quickly gaining an overview of the system state. The output is divided into four columns, name, state, health, and remarks. The state column contains two characters that identify the state of the database, based on Booting (starting up), Running, Stopped, Crashed and Locked (under maintenance). This is followed by the uptime when running. The health column contains the percentage of successful starts and stops, followed by the average uptime. The remarks column can contain arbitrary information about the database state, but usually contains the URI the database can be connected to.


The −c flag shows the most used properties of a database. This includes the state of the database (running, crashed, stopped), whether it is under maintenance or not, the crash averages and uptime statistics. The crash average is the number of times the database has crashed over the last 1, 15 or 30 starts. The lower the average, the healthier the database is.


Triggered by the −l flag, a long listing is used. This listing spans many rows with on each row one property and its value separated by a colon (:). The long listing includes all information that is available.


The −s flag controls which databases are being shown, matching their state. The required argument to this flag can be a combination of any of the following characters. Note that the order in which they are put also controls the order in which the databases are printed. b, r, s, c, and l are used to print a starting up (booting), started (running), stopped, crashed and locked database respectively. The default order which is used when the −s flag is absent, is rbscl.

start [−a] database [database ...]
[−a] database [database ...]
[−a] database [database ...]

Starts, stops or kills the given database, or, when −a is supplied, all known databases. The kill command immediately terminates the database by sending the SIGKILL signal. Any data that hasn’t been committed will be lost. This command should only be used as last resort for a database that doesn’t respond any more. It is more common to use the stop command to stop a database. This will first attempt to stop the database, waiting for exittimeout seconds and if that fails, kill the database. When using the start command, monetdb(1) will output diagnostic messages if the requested action failed. When encountering an error, one should always consult the logfile of monetdbd(1) for more details. For the kill command a diagnostic message indicating the database has crashed is always emitted, due to the nature of that command. Note that in combination with −a the return code of monetdb(1) indicates failure if one of the databases had a failure, even though the operation on other databases was successful.

profilerstart database [database ...]
database [database ...]

Starts or stops the collection of profiling logs for the given database. The property profilerlogpath must be set for the given database, and it should point to a directory where the logs will be gathered. The filenames of the logs have the format: proflog_<database>_YYYY-MM-DD_HH-MM-SS.json where the last part is the date and time when the collection started. Please note that a file recording the pid of the profiler is written in the log directory, therefore each database needs to have a different profilerlogpath value.

monetdb snapshot write dbname

Takes a snapshot of the given database and writes it to stdout.

monetdb snapshot create [-t targetfile] dbname [dbname..]

Takes a snapshot of the given databases. Here, dbname can be either the name of a single database or a pattern such as staging* indicating multiple databases to snapshot. Unless -t is given, the snapshots are written to files named <snapshotdir>/<dbname>_<YYYY><MM><DD>T<HH><MM>UTC<snapshotcompression> where snapshotdir is a monetdbd setting that has to be configured explicitly using monetdbd set and snapshotcompression is another monetdbd setting which defaults to .tar.lz4 or .tar. If -t is given, only a single database can be snapshotted and the snapshot is written to targetfile, a file on the server which must be somewhere under snapshotdir but which does not have to follow any particular naming convention.

monetdb snapshot list [dbname..]

Lists the snapshots for the given databases, or all databases if none is given, showing the snapshot id, the time the snapshot was taken and the (compressed) size of the snapshot file. Only snapshots following the naming convention described under monetdb snapshot create are listed. The snapshot id is of the form dbname@tag where the tags are numbers starting at 1 for the most recent snapshot of a database, 2 for the next most recent, etc. For clarity, the first snapshot for each database shows the full snapshot id (dbname@1) and older snapshots for the same database are listed just as @2, @3, etc.

monetdb snapshot restore [-f] snapshotid [dbname]

Restores a database from the given snapshot, where snapshotid is either a path on the server or name@tag as listed by monetdb snapshot list. The optional dbname argument sets the name of the newly created database. It can be omitted unless snapshotid is a full path. When -f is given, no confirmation is asked when overwriting an existing database.

monetdb snapshot destroy [-f] name@tag..

Delete the listed snapshots from the snapshotdir directory. When -f is given, no confirmation is asked.

monetdb snapshot destroy [-f] -r N dbname..

Delete all but the N latest snapshots for the given databases. Again, dbname can be a pattern such as staging* or even * to work on all snapshotted databases. When -f is given, no confirmation is asked.

get <all | property[,property[,..]]> [database ...]

Prints the requested properties, or all known properties, for the given database. For each property its source and value are printed. Source indicates where the current value comes from, e.g. the configuration file, or a local override.

set property=value database [database ...]

Sets property to value for the given database. For a list of properties, run monetdb get all. Most properties require the database to be stopped when set.

Defines if and how the database is being announced to other monetdbds or not. If not set to yes or no the database is simply announced or not. Using a string, called tag the database is shared using that tag, allowing for more sophisticated usage. For information about the tag format and use, see section REMOTE DATABASES in the monetdbd(1) manpage. Note that this property can be set for a running database, and that a change takes immediate effect in the network.


Defines how many worker threads the server should use to perform main processing. Normally, this number equals the number of available CPU cores in the system. Reducing this number forces the server to use less parallelism when executing queries, or none at all if set to 1.


Each server operates with a given optimizer pipeline. While the default usually is the best setting, for some experimental uses the pipeline can be changed. See the mserver5(1) manpage for available pipelines. Changing this setting is discouraged at all times.


Defines if the database has to be started in readonly mode. Updates are rejected in this mode, and the server employs some read-only optimizations that can lead to improved performance.


Sets the maximum amount of clients that can connect to this database at the same time. Setting this to a high value is discouraged. A multiplex-funnel may be more performant, see MULTIPLEX-FUNNEL below.


Defines how the server interprets literal strings. See the mserver5(1) manpage for more details.

inherit property database [database ...]

Like set, but unsets the database-local value, and reverts to inherit from the default again.

discover [expression]

Returns a list of remote monetdbds and database URIs that were discovered by monetdbd(1). All databases listed can be connected to via the local MonetDB Database Server as if it were local databases using their database name. The connection is redirected or proxied based on configuration settings. If expression is given, only those discovered databases are returned for which their URI matches the expression. The expression syntax is described in the section EXPRESSIONS. Next to database URIs the hostnames and ports for monetdbds that allow to be controlled remotely can be found in the discover list masked with an asterisk. These entries can easily be filtered out using an expression (e.g. "mapi:monetdb:*") if desired. The control entries come in handy when one wants to get an overview of available monetdbds in e.g. a local cluster. Note that for monetdbd to announce its control port, the mero_controlport setting for that monetdbd must be enabled in the configuration file.


help [command]

Shows general help, or short help for a given command.



Shows the version of the monetdb utility.


For various options, typically database names, expressions can be used. These expressions are limited shell-globbing like, where the * in any position is expanded to an arbitrary string. The * can occur multiple times in the expression, allowing for more advanced matches. Note that the empty string also matches the *, hence "de*mo" can return "demo" as match. To match the literal ’*’ character, one has to escape it using a backslash, e.g. "\*".


The monetdb utility returns exit code 0 if it successfully performed the requested command. An error caused by user input or database state is indicated by exit code 1. If an internal error in the utility occurs, exit code 2 is returned.


monetdbd(1), mserver5(1)


monetdbd sjoerd Tue, 04/26/2011 - 12:31


monetdbd − the MonetDB Database Server daemon


monetdbd command [ command_args ] dbfarm


Monetdbd is the MonetDB Database Server daemon. The program is mainly meant to be used as daemon, but it also allows to setup and change the configuration of a dbfarm. The use of monetdbd is either as user-oriented way to configure, start and stop a database farm, or to be started from a startup script, such as from systemd(1) on Linux systems, as part of a system startup.

Monetdbd is the system formerly known as merovingian. It was renamed to monetdbd since the name merovingian proved to be confusing to most regular end-users. Internally, monetdbd uses the name merovingian at many places for historical reasons.

A monetdbd instance manages one local cluster of databases, which is a directory in the system, referred to as the dbfarm. The dbfarm location must always be given as argument to monetdbd.

Within its local cluster monetdbd takes care of starting up databases when necessary, and stopping them either upon request via monetdb(1) or when being shut down. Client database connections are made against monetdbd initially which redirects or proxies the client to the appropriate database process, started on the fly when necessary.

When started, monetdbd runs by default in the background, sending log messages to merovingian.log, until being sent a stop, terminate or interrupt signal, possibly using the stop command of monetdbd.

monetdbd uses a neighbor discovery scheme to detect other monetdbd processes running in the local network. Databases from those remote instances are made available to a locally connecting client. Remote databases never override local databases, and their availability is controlled by the remote monetdbd process. See also the sharing capabilities of monetdb(1) and the REMOTE DATABASES section below.


The commands for monetdbd are create, start, stop, get, set, version, and help. The commands facilitate initializing a dbfarm, starting and stopping the MonetDB Database Server, and retrieving or setting options.

Initializes a new database farm, such that a MonetDB Database Server can be started on that location. All necessary directories are attempted to be created, and an initial properties file is created in the directory itself. dbfarm must be a location addressable in the local filesystem hierarchy.

start [−n] dbfarm

Starts monetdbd, the MonetDB Database Server, on the given dbfarm. When the −n flag is given, monetdbd will not fork into the background, but instead remain attached to the calling environment, until given a stop signal.

stop dbfarm

Sends a stop signal to the monetdbd process responsible for the given dbfarm. If the exittimeout value is non-zero (see below), all mserver processes will be sent a termination signal. The current process will wait for the manager process to terminate, but sends a SIGKILL signal if waiting takes longer than 5 seconds more than the value of exittimeout. If exittimeout is negative, both monetdbd processes involved will wait until the servers have all terminated and no extra signals are sent.

get <all | property[,property[,..]]> dbfarm

Prints the requested properties, or all known properties, for the given dbfarm. For each property, its value is printed. Some properties are virtual, and given for information purposes only, they cannot be modified using the set command.

set property=value dbfarm

Sets property to value for the given database. For a list of properties, run monetdbd get all. Some properties require a restart of the MonetDB Database Server in order to take effect. The set command, will however always write the property, and tell the running monetdbd to reload the properties file (if running). For an explanation of the properties, see the CONFIGURATION section below.


Monetdbd reads its properties from the .merovingian_properties file inside the dbfarm. This file is created by the create command. This file is not meant to be edited manually, instead it should be updated using the set command. The following properties can be set:

This property points to the file where all log messages are written to. It is relative to the dbfarm directory, but can be absolute to point to e.g. another medium. Changing this property takes effect immediately at runtime.


Monetdbd stores the process ID of the background server in the file pointed to by this property. The same rules apply as for the logfile property.


For faster access, monetdbd uses UNIX domain sockets for its control mechanism and regular database connections. The sockets are placed as files in the filesystem hierarchy. The sockdir property controls in which directory they are placed. In general this setting should not be changed.


This property specifies which TCP port monetdbd should listen to for connection requests. Defaults to 50000.


This property specifies an address that is allowed to connect to the server. The following possibilities exist:

The server only listens on the IPv4 and IPv6 loopback interface (if available). This is the default.

The server only listens on the IPv4 loopback interface.


The server only listens on the IPv6 loopback interface.


The server listens on all available IPv4 and IPv6 interfaces.

The server listens on all available IPv4 interfaces.


The server listens on all available IPv6 interfaces.


The server listens on the interface designated by hostname which is looked up using the normal hostname lookup facilities.


For remote management of monetdbd, the control property specifies whether or not to enable remote management. Note that for remote management, a passphrase is required, see below. It defaults to false for security reasons. Changing this property takes effect immediately at runtime.


To control monetdbd from a remote machine, a passphrase is necessary, to be given to monetdb(1). The passphrase can be either given as hashed value prefixed by the hash type in curly braces (e.g. {SHA512}xxx...) or as plain text value which will be hashed automatically. Note that the only hash accepted is the one specified at configure time, which is SHA512. Changing this property takes effect immediately at runtime.


This property specifies where the monetdb snapshot create command stores its snapshots. There is no default value. If unset, no snapshots can be created.


This property specifies whether database snapshots created by monetdb snapshot create are compressed, and if so, using which algorithm. The default value is .tar.lz4 if LZ4 compression is available, or .tar otherwise. Other supported values are, if available, .tar.gz, .tar.xz, and .tar.bz2. These more efficient but much slower compression algorithms are usually not recommended for backups of large databases because it would take enormous amounts of time.


Specifies whether neighbor discovery is to be enabled using UDP broadcasts or not. The broadcasts are done on the same portnumber as the port setting.


Monetdbd publishes locally available databases to others periodically. The interval used here, defined in seconds, depends on the time-to-live of the databases before they need to get refreshed. The default is 600 seconds (10 minutes), which should keep traffic in your network fairly low. Additions and removals are processed immediately regardless of this timeout. If you are in a network environment where physical network links disappear often, you may want to decrease this value to more quickly remove no longer reachable databases.


If monetdbd stops a running mserver, for example in response to a monetdb stop command or when monetdbd itself is shutting down, it first sends the mserver a SIGTERM signal to trigger a graceful shutdown. If that takes more than exittimeout seconds, SIGKILL is sent as a last resort. This may cause (partial) data loss in that transactions may not be able to complete (all completed transactions, whether reported back or not, should be save). A negative time-out value value means the second signal (SIGKILL) will not be sent, but instead all mserver processes will be waited for. A time-out value of 0 means no mservers will be shut down, and hence they will continue to run after monetdbd has shut down. Note that this particular configuration is extremely inconvenient. The default time-out is 60 seconds. If your databases are rather large and you find your databases consistently being killed by monetdbd upon shutdown, you may want to increase this time-out. Changing this property takes effect immediately at runtime.


monetdbd has two ways in which it can "attach" a connecting client to the target database. The first method, redirect, uses a redirect sent to the client with the responsible mserver process. The second method, proxy, proxies the client to the mserver over monetdbd. While redirect is more efficient, it requires the connecting client to be able to connect to the mserver. In many settings this may be undesirable or even impossible, since a wide range of open ports and routing are necessary for this. In such case the proxy technique of monetdbd is a good solution, which also allows a monetdbd instance on the border of a network to serve requests to nodes in the local (unreachable) network. Note that for local databases, the proxy method uses a UNIX domain socket feature to pass file-descriptors to the local mserver. This effectively is as efficient as the redirect approach, but still hides away the mservers properly behind monetdbd. Hence, in practice it is only relevant for connections to remote databases to use redirects instead of proxies. Changing this property takes effect immediately at runtime.


The neighbor discovery capabilities of monetdbd allow a user to contact a remote database transparently, as if it were a local database. By default, all local databases are announced in the network, such that neighbors can pick them up to make them available for their local users. This feature can be disabled globally, or on database level. For the latter, the monetdb(1) utility can be used to change the share property of a database.

While neighbor discovery in itself is sufficient to locate a database in a cluster, it is limited in expressiveness. For instance, database names are assumed to be unique throughout the entire system. This means local databases overshadow remote ones, and duplicate remote entries cannot be distinguished. To compensate for this, monetdbd allows to adds a tag to each database that is being shared. This tag is sent in addition to the database name, and only understood by other monetdbds.

Tags are arbitrary ASCII-strings matching the pattern [A−Za−z0−9./]+. There are no assumed semantics in the tag, which allows for multiple approaches when using the tag. The tag is always used in combination with the database name. For this, the ‘/’ character is used as separator, which hence suggests the user to use that character as separator for multilevel tags. Monetdbd allows common path globbing using ‘*’ on tags, which allows for many use-cases. Consider for instance the following three databases with their tag:


A default match has implicit ‘/*’ added to the search, making more generic search strings match more specific ones. Hence, a connect with database dbX is the same as dbX/* and hence matches dbX/master/tableQ. Similar, a database connect for */master matches the same database as before. Note that the implicit ‘/*’ is not added if that would cause no matches, such as for */master/tableQ which would return all masters for tableQ, which in our hypothetical example is only dbX. In contrast, a database connect for */slave/tableQ matches with either dbY or dbZ. Monetdbd returns the two options to the client in a round-robin fashion, such that subsequent connects for the same pattern result in a load-balanced connect to either of both databases.

With tags in use, one can possibly make distinction between databases, if setup like that. The previous example could hence also be setup like this:


Connecting to tableQ/slave would now return either of both databases even though they are not unique (apart from the host they are located on, which is not shown in the example). While being confusing for humans, for monetdbd it is the same situation as in the previous example. However, because globbing allows to make things easier to understand, tags for both slaves could be changed to slaveX or slave/X and use the necessary pattern to match them. It is up to the user to decide how to use the tags.


Monetdbd implements multiplex-funnel capabilities. As the name suggests two techniques are combined, the multiplexer and the funnel.

The funnel capability limits the access to the database to one client at a time. That is, if multiple clients connect to the funnel, their queries will be serialized such that they are executed one after the other. An effect of this approach is that clients no longer have an exclusive channel to the database, which means that individual queries from one client may have been interleaved with queries from others. This most notably makes SQL transaction blocks unreliable with a funnel. The funnel, hence, is meant to scale down a large amount of clients that perform short-running (read-only) queries, as typically seen in web-based query loads.

When a funnel is defined to use multiple databases, the funnel adds a multiplexer to its query channel. A multiplex-funnel sends each query to all of the defined databases. This behavior can be quite confusing at first, but proves to be useful in typical sharding configurations, where in particular simple selection queries have to be performed on each of the shards. The multiplexer combines the answers from all defined databases in one single answer that it sends back to the client. However, this combining is without any smart logic, that is, the multiplexer does not evaluate the query it is running, but just combines all answers it receives from the databases. This results in e.g. as many return tuples for a SELECT COUNT(*) query, as there are databases defined.

Due to the two above mentioned characteristics, a multiplex-funnel has some limitations. As mentioned before, transactions over multiple queries are likely not to result in the desired behavior. This is due to each query to the funnel is required to be self-contained. Further, since for each query, the results from multiple servers have to be combined into one, that query must only return a single response, i.e. multi-statement queries are most likely causing the funnel to respond with an error, or return garbled results. Last, the size of each query is limited to currently about 80K. While this size should be sufficient for most queries, it is likely not enough for e.g. COPY INTO statements. Apart from the data transfer implications, such statements should not be used with the funnel, as the results will be undefined due to the limited query buffer. Applications using the funnel should aim for short and single-statement queries that require no transactions.

See the create command in the monetdb(1) man-page for details on how to setup a multiplex-funnel.


Monetdbd acts upon a number of signals as is common for a daemon.

Any of these signals make monetdbd enter the shutdown sequence. This sequence involves cleanly shutting down listener sockets, shutting down all started databases and finally terminating itself.


When this signal is received by monetdbd it will reopen the logfile as pointed to by the logfile setting. Before it reopens the logfile, it will re-read the properties file from the dbfarm, which might result in opening a different file to continue logging.


Monetdbd returns exit code 0 if it was able to successfully perform the requested action, e.g. start, stop, etc. When an error occurs during the action, that prevents monetdbd from successfully performing the action, the exit code 1 is returned.


monetdb(1), mserver5(1)


mserver5 sjoerd Tue, 04/26/2011 - 12:35


mserver5 − the MonetDB server version 5


mserver5 [ options ]


Mserver5 is the current MonetDB server that performs all processing on request of clients for a certain database.

Note that while mserver5 is the process that does the actual work, it is usually more common to start, monitor and connect to the mserver5 process through monetdbd(1).

This man-page describes the options that mserver5 understands. It is intended for people who really need to work with mserver5 itself. In regular cases, the programs monetdbd(1) and monetdb(1) control the many options, and allow to adjust them to appropriate values where sensible. For normal usage, it is preferred to apply any configuration through these programs.


When the build-time configuration did not disable this, a mserver5 process presents the user with a console prompt. On this prompt, MAL commands can be executed. The architecture is setup to handle multiple streams of requests. The first thread started represents the server, which is the console prompt, reading from standard input and writing to standard output.

The server thread started remains in existence until all other threads die. The server is stopped by sending it a termination signal (SIGINT, SIGTERM, SIGQUIT).


Mserver5 can be started with options as arguments.

Path where mserver5 should find a database. Shorthand for option gdk_dbpath. Default value: /var/monetdb5/dbfarm/demo.


Path where mserver5 should store transient data. Default value is the value of the −−dbpath option. If the value of path is in-memory, transient data is not stored on disk at all but kept in memory at all times.


File name for the trace log file for mserver5. Default value is the file mdbtrace.log inside the directory specified with the −−dbpath option.


Config file to read options from. This file can contain all options as can be set with the −−set flag. See CONFIG FILE FORMAT.


Allow only a single user at a time.


The database is opened in read-only mode.

−−set option=value

Set individual configuration option. For possible options, see PARAMETERS sections.




Print list of options.



Print version and compile configuration.


Run mserver5 in-memory. No data will be written to disk. The name of the database that a client can connect to is in-memory.


Set debug level. This is mostly for debugging purposes. The value is an integer, which can be (a bit-wise OR of):
1 = THRDMASK = thread-specific debug output
2 = CHECKMASK = property enforcing on new BATs
8 = PROPMASK = property checking on all values:
tells about wrongly set properties
16 = IOMASK = major IO activity
32 = BATMASK = BAT handling
128 = PARMASK = Thread management
512 = TMMASK = Transaction management
1024 = TEMMASK = Locks and Triggers
4096 = PERFMASK = BBP Performance (?)
8192 = DELTAMASK = Delta debugging (?)
16384 = LOADMASK = Module loading
1048576 = ACCELMASK = Accelerator debugging
2097152 = ALGOMASK = show low level algorithm chosen
16777216 = NOSYNCMASK = disable forcefully synchronizing files
to disk. If this flag is set, there is
no guarantee that the database remains
consistent after a crash. DO NOT USE
(unless you really don’t care about your
33554432 = DEADBEEFMASK = disable "cleaning" of freed memory
in GDKfree() which only happens in a
debug build (i.e. with assertions
enabled) e.g., for performance
67108864 = ALLOCMASK = exhaustive GDK malloc & free tracing
for debugging (GDK developers, only)
134217728 = OPTMASK = trace the actions, decisions and
effects of MAL optimizers
268435456 = HEAPMASK = trace/debug HEAPextend;
used only for development & debugging
536870912 = FORCEMITOMASK = forcefully activate mitosis even on
small tables, i.e., split small tables
in as many (tiny) pieces as there are
cores (threads) available;
this allows us to test mitosis
functionality without requiring large
data sets (— at the expense of a
potentially significant interpretation
overhead for unnecessarily large plans);
used only for development & testing;
set automatically by
The value together with the = sign is optional. If not specified, it defaults to 1. In the short form −d, the value, if present, must immediately (i.e. without space) follow the option. The values of multiple instances of this flag are OR-ed together.


Equivalent to −−debug=(ALGOMASK).


Equivalent to −−debug=(FORCEMITOMASK | NOSYNCMASK).


Equivalent to −−debug=(HEAPMASK).




Equivalent to −−debug=(IOMASK | PERFMASK).



Equivalent to −−debug=(ALLOCMASK).


Equivalent to −−debug=(LOADMASK).


Equivalent to −−debug=(DEADBEEFMASK).


Equivalent to −−debug=(CHECKMASK | PROPMASK | BATMASK).


Equivalent to −−debug=(THRDMASK | PARMASK).


Equivalent to −−debug=(TMMASK | DELTAMASK | TEMMASK).


Read an unencrypted password from standard input and use it to set the password for the monetdb administrator user, initialize the database, and exit. If the database was already initialized, the administrator password is not changed. This option is used by monetdbd(1) when creating a new database with an administrator password and should not be used otherwise.


Mserver5 instructs the GDK kernel through the MAL (MonetDB Assembler Language) language. MonetDB 5 contains an extensive optimiser framework to transform MAL plans into more optimal or functional (e.g. distributed) plans. These parameters control behaviour on the MAL level.

The authorisation tables inside mserver5 can be encrypted with a key, such that reading the BATs does not directly disclose any credentials. The monet_vault_key setting points to a file that stores a secret key to unlock the password vault. It can contain anything. The file is read up to the first null-byte (’\0’), hence it can be padded to any length with trailing null-bytes to obfuscate the key length. Generating a key can be done for example by using a tool such as pwgen and adding a few of the passwords generated. Make sure not to choose a too small key. Note that on absence of a vault key file, some default key is used to encrypt the authorisation tables. Changing this setting (effectively changing the key) for an existing database makes that database unusable as noone is any longer able to login. If you use monetdbd(1), a per-database vault key is set.


Controls how many client slots are allocated for clients to connect. This settings limits the maximum number of connected clients at the same time. Note that MonetDB is not designed to handle massive amounts of connected clients. The funnel capability from monetdbd(1) might be a more suitable solution for such workloads. Default 64.


The name of the UNIX domain socket file on which the server will listen for connections. If the name contains the substring ${PORT}, that part will be replaced by the decimal representation of the TCP/IP port (option mapi_port). This is especially useful if the port was specified as 0. Note, there is usually a severe system-imposed length limitation on the name of the file.


The TCP/IP port number on which the server will listen for connections. This is only used if the value of the mapi_listenaddr option is not equal to none. Default 50000. If the value is 0, the server will use a so called ephemeral port, i.e. one that is assigned by the system. After successfully starting to listen to a port, the value of the port can be retrieved from the file .conn inside the database (−−dbpath) directory.


The TCP/IP interface on which the server will listen for connections. Possibilites are:

The server listens only on the IPv4 and IPv6 loopback interface. This is the default.

The server listens only on the IPv4 loopback interface.




The server listens only on the IPv6 loopback interface.




The server listens on all IPv4 and IPv6 interfaces.

The server listens on all IPv4 interfaces.




The server listens on all IPv6 interfaces.




The server will not listen on any TCP/IP interface (you need to use the UNIX domain socket interface).


The server will listen on the interface designated by hostname which is looked up using the normal hostname lookup facilities.


The SQL component of MonetDB 5 runs on top of the MAL environment. It has its own SQL-level specific settings.

Enable debugging using a mask. This option should normally be disabled (0). Default: 0.


The default SQL optimizer pipeline can be set per server. See the optpipe setting in monetdb(1) when using monetdbd. During SQL initialization, the optimizer pipeline is checked against the dependency information maintained in the optimizer library to ensure there are no conflicts and at least the pre-requisite optimizers are used. The setting of sql_optimizer can be either the list of optimizers to run. Default: default_pipe.
The following are possible pipes to use:

The minimal pipeline necessary by the server to operate correctly. minimal_pipe=inline,remap,deadcode,multiplex,generator,profiler,candidates,garbageCollector


The default pipeline contains the mitosis-mergetable-reorder optimizers, aimed at large tables and improved access locality. default_pipe=inline,remap,costModel,coercions,aliases,evaluate,emptybind,deadcode,pushselect,aliases,mitosis,mergetable,aliases,constants,commonTerms,projectionpath,deadcode,reorder,matpack,dataflow,querylog,multiplex,generator,profiler,candidates,postfix,deadcode,wlc,garbageCollector


The no_mitosis pipeline is identical to the default pipeline, except that optimizer mitosis is omitted. It is used mainly to make some tests work deterministically, and to check/debug whether "unexpected" problems are related to mitosis (and/or mergetable). no_mitosis_pipe=inline,remap,costModel,coercions,aliases,evaluate,emptybind,deadcode,pushselect,aliases,mergetable,aliases,constants,commonTerms,projectionpath,deadcode,reorder,matpack,dataflow,querylog,multiplex,generator,profiler,candidates,postfix,deadcode,wlc,garbageCollector


The sequential pipeline is identical to the default pipeline, except that optimizers mitosis & dataflow are omitted. It is use mainly to make some tests work deterministically, i.e., avoid ambigious output, by avoiding parallelism. sequential_pipe=inline,remap,costModel,coercions,aliases,evaluate,emptybind,deadcode,pushselect,aliases,mergetable,aliases,constants,commonTerms,projectionpath,deadcode,reorder,matpack,querylog,multiplex,generator,profiler,candidates,postfix,deadcode,wlc,garbageCollector


Enable embedded Python. This means Python code can be called from SQL. The value is true or 3 for embedded Python 3. Note that by enabling embedded Python, users of the server are allowed to execute arbitrary Python code, and are therefore able to read and modify all data that the server process has access to.


Enable embedded R. This means R code can be called from SQL. Note that by enabling embedded R, users of the server are allowed to execute arbitrary R code, and are therefore able to read and modify all data that the server process has access to.


Enable embedded C. This means C code can be called from SQL. The C code will first be compiled and then executed. This means a C compiler must be available. Note also that by enabling embedded C, users of the server are allowed to execute arbitrary C code, and are therefore able to read and modify all data that the server process has access to. In addition, if the C code causes a crash, all bets are off.


The boolean option raw_strings controls how the sql scanner interprets string literals. If the value is false then strings are interpreted as if they were delimited with E-quotes, that is strings are interpreted as C strings and backslash characters are needed to escape special characters. If the value is true then strings are interpreted as if they were delimited with R-quotes, that is all characters are interpreted literally. Single quote characters need to be doubled inside strings. The default value is false.


The configuration file readable by mserver5 consists of parameters of the form "name=value". The file is line-based, each newline-terminated line represents either a comment or a parameter. Only the first equals sign in a parameter is significant. Whitespace before or after the first equals sign is not stripped. Trailing whitespace in a parameter value is retained verbatim. Any line beginning with a hash (#) is ignored, as are lines containing only whitespace. The values following the equals sign in parameters are all a string where quotes are not needed, and if written be part of the string.


monetdbd(1), monetdb(1), mclient(1)