A comprehensive list of environment variables that are directly or indirectly used by GT.M are as follows:

EDITOR is a standard system environment variable that specifies the full path to the editor to be invoked by GT.M in response to the ZEDit command (defaults to vi, if $EDITOR is not set).

GTMCI specifies the call-in table for function calls from C code to M code.

GTMXC_gpgagent specifies the location of gpgagent.tab. By default, GT.M places gpgagent.tab in the $gtm_dist/plugin/ directory. GTMXC_gpgagent is used by pinentry-gtm.sh and is meaningful only if you are using Gnu Privacy Guard version 2.

LC_CTYPE is a standard system environment variable used to specify a locale. When $gtm_chset has the value "UTF-8", $LC_CTYPE must specify a UTF-8 locale (e.g., "en_US.utf8").

LC_ALL is a standard system environment variable used to select a locale with UTF-8 support. LC_ALL is an alternative to LC_TYPE, which overrides LC_TYPE and has a more pervasive effect on other aspects of the environment beyond GT.M.

LD_LIBRARY_PATH (LIBPATH on AIX) is a standard system environment variable used to modify the default library search path. Use this extension when GT.M relies on custom compiled libraries that do not reside in the default library search path. For example ICU, GPG, OpenSSL and/or zlib libraries.

TZ is a standard system environment variable that specifies the timezone to be used by a GT.M process, if they are not to use the default system timezone. GT.M uses the system clock for journal time stamps on the assumption it reflects UTC time.

gtmcompile specifies the initial value of the $ZCOmpile ISV. The SET command can alter the value of $ZCOMPILE in an active process.

gtmcrypt_config specifies the location of the configuration file required for database encryption, Sequential file, PIPE, and FIFO device encryption and/or TLS support. A configuration file is divided into two sections: database and TLS. The "database" section contains a list of database files and their corresponding key files. You do not need to add a database section if you are not using an encrypted database, or a "tls" section if you are not using TLS for replication or sockets. The tls section provides information needed for OpenSSL (in the reference plugin implementation) or other encryption package, such as the location of root certification authority certificate in PEM format and leaf-level certificates with their corresponding private key files. Note that the use of the gtmcrypt_config environment variable requires prior installation of the libconfig package.

gtmcrypt_FIPS specifies whether the plugin reference implementation should attempt to use either OpenSSL or Libgcrypt to provide database encryption that complies with FIPS 140-2. When the environment variable $gtmcrypt_FIPS is set to 1 (or evaluates to a non-zero integer, or any case-independent string or leading substring of "TRUE" or "YES"), the plugin reference implementation attempts to use libgcrypt (from GnuPG) and libcrypto (OpenSSL) in "FIPS mode." Note that to comply with FIPS 140-2 you should be knowledgeable with that standard and take many steps beyond setting this environment variable. By default GT.M does not enforce "FIPS mode."

gtmgbldir specifies the initial value of the $ZGBLDIR ISV. $ZGBLDIR identifies the global directory. A global directory maps global variables to physical database files, and is required to access M global variables. Users who maintain multiple global directories use this environment variable to conveniently choose one to use from the time of process startup. To automate this definition, define gtmgbldir in the user's login file. The SET command can alter the value of $ZGBLDIR in an active process.

gtmroutines specifies the initial value of the $ZROutines ISV, which specifies where to find object and source code. The SET command can alter the value of $ZROUTINES in an active process.

gtmtls_passwd_<label> specifies the obfuscated password of the encrypted private key pair. You can obfuscate passwords using the 'maskpass' utility provided along with the encryption plugin. If you choose to use unencrypted private keys, set the gtmtls_passwd_<label> environment variable to a non-null dummy value; this prevents inappropriate prompting for a password.

gtmver (not used by GT.M directly) - The current GT.M version. The gtmprofile script uses $gtmver to set other environment variables.

gtm_aio_nr_events: For Linux x86_64, the gtm_aio_nr_events environment variable controls the number of structures a process has per global directory to manage asynchronous writes, and therefore determines the number of concurrent writes a process can manage across all regions within a global directory. If not specified, the value controlled by gtm_aio_nr_events defaults to 128. If a process encounters a situation where it needs to perform an asynchronous write, but has no available slots with which to manage an additional one, it either falls back to synchronous writing if the write is blocking other actions, and otherwise defers the write until a slot becomes available as other writes complete. Linux allocates the structures on a system-wide basis with the setting of /proc/sys/fs/aio-max-nr. Therefore you should configure this parameter to account for the needs (as determined by gtm_aio_nr_events or the default) of all processes using asynchronous I/O. When processes use multiple global directories with asynchronous I/O, their need for the system resources increases accordingly. For example, if an environment runs 10,000 processes each of which open two global directories and /proc/sys/fs/aio-max-nr is set to a value of 200,000 then gtm_aio_nr_events needs to be set to a value <= 200,000 / (10,000 * 2) = 10. Conversely if gtm_aio_nr_events is set to a value of 20, then aio-max-nr needs to be bumped up to (10,000 * 2 * 20) = 400,000. GT.M captures the number of errors encountered when attempting to write database blocks for a region, and, barring problems with the storage subsystem, hitting an asynchronous write limit would constitute primary (probably only) contribution to that value, which you can access with $$^%PEEKBYNAME("sgmnt_data.wcs_wterror_invoked_cntr",<region>)

gtm_autorelink_ctlmax specifies the maximum number of entries for unique routine names in the relink control file created by a process for any directory, with a minimum of 1,000, a maximum of 16,000,000 and a default of 50,000 if unspecified. If a specified value is above or below the allowed range, the process logs the errors ARCTLMAXHIGH or ARCTLMAXLOW respectively in the syslog, and uses the nearest acceptable limit instead. MUPIP RCTLDUMP and ZSHOW "A" outputs include the maximum number of unique routine names available in a relink control file. If the maximum number of entries for unique routine names is exceeded, it triggers a relinkctl integrity-check to ensure that all pointers and indexes are within the shared memory bounds.

gtm_autorelink_keeprtn:

When gtm_autorelink_keeprtn is set to 1, t[rue], or y[es] , exiting processes leave auto-relinked routines in shared memory. When the environment variable gtm_autorelink_keeprtn is undefined, 0, f[alse] or n[o], exiting processes purge auto-relinked routines in shared memory if no other processes are using them. Regardless of the value of gtm_autorelink_keeprtn, the Operating System removes an auto-relink shared memory repository when there are no processes accessing it.

All values are case-independent. When gtm_autorelink_keeprtn is defined and TRUE:

gtm_autorelink_shm specifies the size (in MiB) of an initial Rtnobj shared memory segment used by the auto-relink facility. If the value of gtm_autorelink_shm is not a power of two, GT.M rounds the value to the next higher integer power of two. If the first object (.o) file does not fit in a new Rtnobj segment, GT.M rounds the allocation up to the smallest integer power of two required to make it fit. When GT.M needs room for object files, and existing Rtnobj segments have insufficient free space, it creates an additional shared memory segment, double the size of the last. Note that when hugepages are enabled, the actual Rtnobj shared memory size might be more than that requested implicitly or explicitly through $gtm_autorelink_shm.

gtm_badchar specifies the initial setting that determines whether GT.M should raise an error when it encounters an illegal UTF-8 character sequence. This setting can be changed with a VIEW "[NO]BADCHAR" command, and is ignored for I/O processing and in M mode.

gtm_baktmpdir specifies the directory where MUPIP BACKUP creates temporary files. If $gtm_baktmpdir is not defined, GT.M uses the deprecated $GTM_BAKTMPDIR environment variable. If both $gtm_baktmpdir and $GTM_BAKTMPDIR are not defined, MUPIP BACKUP creates temporary files as follows:

All processes performing updates during an online BACKUP must have the use the same directory and have write access.

gtm_boolean specifies the initial setting that determines how GT.M compiles Boolean expression evaluation (expressions evaluated as a logical TRUE or FALSE). If gtm_boolean is undefined or evaluates to an integer zero (0), GT.M behaves as it would after a VIEW "NOFULL_BOOLEAN" and compiles such that it stops evaluating a Boolean expression as soon as it establishes a definitive result . Note that:

gtm_chset determines the mode in which GT.M compiles and operates. If it has a value of "UTF-8" GT.M assumes that strings are encoded in UTF-8. In response to a value of "M" (or indeed anything other than "UTF-8"), GT.M treats all 256 combinations of the 8 bits in a byte as a single character.

gtm_chset_locale (z/OS only) specifies the locale for UTF-8 operations on z/OS.

gtm_collate_n specifies the shared library holding an alternative sequencing routine when using non-M standard (ASCII) collation. The syntax is gtm_collate_n=pathname where n is an integer from 1 to 255 that identifies the collation sequence, and pathname identifies the shared library containing the routines for that collation sequence.

gtm_coredump_filter: In Linux x86_64 if the environment variable gtm_coredump_filter is defined, it specifies the mappings of the process address space for a GT.M process, with the bits having the same meaning as those specified for /proc/{pid}/coredump_filter in "man 5 core". If unspecified, GT.M uses a value of 0x73; a value of -1 prevents GT.M from modifying the coredump_filter value. A running process can change its coredump_filter by writing to the file /proc/{pid}/coredump_filter, and can query the current value by reading that file.

gtm_crypt_plugin: If the environment variable gtm_crypt_plugin is defined and provides the path to a shared library relative to $gtm_dist/plugin, GT.M uses $gtm_dist/plugin/$gtm_crypt_plugin as the shared library providing the plugin. If $gtm_crypt_plugin is not defined, GT.M expects $gtm_dist/plugin/libgtmcrypt.so to be a symbolic link to a shared library providing the plugin. The expected name of the actual shared library is libgtmcrypt_cryptlib_CIPHER.so (depending on your platform, the actual extension may differ from .so), for example, libgtmcrypt_openssl_AESCFB. GT.M cannot and does not ensure that the cipher is actually AES CFB as implemented by OpenSSL.

gtm_custom_errors specifies the complete path to the file that contains a list of errors that should automatically stop all updates on those region(s) of an instance which have the Instance Freeze mechanism enabled.

gtm_db_create_ver directs MUPIP CREATE to create GT.M V6.3-014 compatible database file(s) when the environment variable is set to "6" or "V6".

gtm_db_startup_max_wait specifies how long to wait for a resolution of any resource conflict when they first access a database file. GT.M uses semaphores maintained using UNIX Inter-Process Communication (IPC) services to ensure orderly initialization and shutdown of database files and associated shared memory. Normally the IPC resources are held in an exclusive state only for very brief intervals. However, under unusual circumstances that might include extremely large numbers of simultaneous database initializations, a long-running MUPIP operation involving standalone access (like INTEG -FILE or RESTORE), an OS overload or an unpredicted process failure the resources might remain unavailable for an unanticipated length of time. $gtm_db_startup_max_wait specifies how long to wait for the resources to become available:

The default value for the wait if $gtm_db_startup_max_wait is not defined is 96 seconds.

gtm_dist specifies the path to the directory containing the GT.M system distribution. gtm_dist must be defined for each user. If you are not using the gtm script or sourcing gtmprofile, consider defining gtm_dist in the login file or as part of the default system environment. In UTF-8 mode, the gtm_dist environment variable specifies the path to the directory containing the GT.M system distribution for Unicode® support. The distribution for UTF-8 mode is located in subdirectory utf8 under the GT.M distribution directory. For example, if the GT.M distribution is in /usr/lib/fis-gtm/V6.1-000_x86, set gtm_dist to point to /usr/lib/fis-gtm/V6.0-003_x86/utf8 for UTF-8 mode. Correct operation of GT.M executable programs requires gtm_dist to be set correctly.

gtm_dmterm specifies a [NO]DMTERM state at process initiation where application setting applied to $PRINCIPAL also apply to direct mode interactions; a case-insensitive value of "1", "yes", or "true" establishes a DMTERM state at process initiation where direct mode uses default terminal characteristics and ignores application settings for $PRINCIPAL; all other values, including no value, result in the default VIEW "NODMTERM" behavior.

gtm_env_translate specifies the path to a shared library to implement the optional GT.M environment translation facility that can assist in resolving extended global referernces.

gtm_etrap specifies an initial value of $ETRAP to override the default value of "B" for $ZTRAP as the base level error handler. The gtmprofile script sets gtm_etrap to "Write:(0=$STACK) ""Error occurred: "",$ZStatus,!" which you can customize to suit your needs.

gtm_extract_nocol specifies whether a MUPIP JOURNAL -EXTRACT (when used without -RECOVER or -ROLLBACK) on a database with custom collation should use the default collation if it is not able to read the database file. In a situation where the database file is inaccessible or the replication instance is frozen with a critical section required for the access held by another process and the environment variable gtm_extract_nocol is defined and evaluates to a non-zero integer or any case-independent string or leading substrings of "TRUE" or "YES", MUPIP JOURNAL -EXTRACT issues the DBCOLLREQ warning and proceeds with the extract using the default collation. If gtm_extract_nocol is not set or evaluates to a value other than a positive integer or any case-independent string or leading substrings of "FALSE" or "NO", MUPIP JOURNAL -EXTRACT exits with the SETEXTRENV error.

gtm_nofflf specifies the default WRITE # behavior for STREAM and VARIABLE format sequential files. If it is set to 1, Y[ES] or T[RUE], WRITE # writes only a form-feed <FF> character in conformance to the M standard. If it is not defined or set to 0, NO, or FALSE, WRITE # writes <FF><LF> characters. The [NO]FFLF deviceparameter for USE and OPEN commands takes precedence over any value of gtm_nofflf.

gtm_gdscert specifies the initial setting that controls whether GT.M processes should test updated database blocks for structural damage. If it is defined, and evaluates to a non-zero integer or any case-independent string or leading substrings of "TRUE" or "YES", GT.M performs block-level integrity check on every block as a process commits it. Within a running process, VIEW "GDSCERT":value controls this setting By default, GT.M does not check database blocks for structural damage, because the impact on performance is usually unwarranted.

gtm_gvdupsetnoop specifies the initial value that determines whether a GT.M process should enable duplicate SET optimization. If it is defined, and evaluates to a non-zero integer or any case-independent string or leading substrings of "TRUE" or "YES", when a SET command does not change the value of an existing node, GT.M does not perform the update or execute any trigger code specified for the node. Within a running process, VIEW "GVDUPSETNOOP":value controls this behavior. By default, GT.M enables this optimization.

gtm_hugetlb_shm specifies the initial value that determines whether a GT.M process should use huge pages to back shared memory. If it is defined, and evaluates to a non-zero integer or any case-independent string or leading substrings of "TRUE" or "YES" in a GT.M process creating shared memory, GT.M attempts to back all such shared memory segments with huge pages, using the default huge page size. If huge pages cannot be used, GT.M tries to back the shared memory with base pages instead, and attempts to pin the shared memory if requested with $gtm_pinshm.

gtm_hupenable specifies the initial value that determines whether a GT.M process should recognize a disconnect signal from a PRINCIPAL device that is a terminal. If it is defined, and evaluates to a non-zero integer or any case-independent string or leading substrings of "TRUE" or "YES", the process receives an TERMHANGUP error if the O/S signals that the terminal assigned to the process as the PRINCIPAL device has disconnected. Within a running process, USE $PRINCIPAL:[NO]HUP[ENABLE] controls this behavior. By default, GT.M ignores such a signal, but a process that ignores the signal may subsequently receive an IOEOF or a TERMWRITE error from an attempt to respectively READ from, or WRITE to the missing device. GT.M terminates a process that ignores more than one of these messages and, if the process is not in Direct Mode, sends a NOPRINCIO message to the operator log.

gtm_icu_version specifies the MAJOR VERSION and MINOR VERSION numbers of the desired ICU. For example "3.6" denotes ICU-3.6. If $gtm_chset has the value "UTF-8", GT.M requires libicu with version 3.6 or higher. If you must chose between multiple versions of libicu or if libicu has been compiled with symbol renaming enabled, GT.M requires gtm_icu_version to be explicitly set. Please see the section on "Configuring and operation GT.M with Unicode® Support" for more information,

gtm_ipv4_only specifies whether a Source Server should establish only IPv4 connections with a Receiver Server or sockets associated with a SOCKET device. If it is defined, and evaluates to a non-zero integer, or any case-independent string or leading substring of "TRUE" or "YES", the Source Server establishes only IPv4 connections with the Receiver Server. gtm_ipv4_only is useful for environments where different server names are not used for IPv4 and IPv6 addresses and the Source Server connects to a Receiver Server running a GT.M version prior to V6.0-003.

gtm_jnl_release_timeout specifies the number of seconds that a replicating Source Server waits when there is no activity on an open journal file before closing it. The default wait period is 300 seconds (5 minutes). If $gtm_jnl_release_timeout specifies 0, the Source Server keeps the current journal files open until shutdown. The maximum value for $gtm_jnl_release_timeout is 2147483 seconds.

gtm_keep_obj specifies whether the gtminstall script should delete the object files from the GT.M installation directory. If gtm_keep_obj is set to "Y", the gtminstall script leaves object files; by default, gtminstall deletes object files after archiving them in a shared library.

gtm_lct_stdnull specifies whether a GT.M process should use standard collation for local variables with null subscripts or legacy GT.M collation.

gtm_link specifies the initial setting that determines whether GT.M permits multiple versions of the same routine to be active at different stack levels of the M virtual machine. The VIEW "LINK":"[NO]RECURSIVE" command modifies this in an active process. If gtm_link is set to "RECURSIVE", auto-relink and explicit ZLINK commands links a newer object even when a routine with the same name is active and available in the current stack. When a process links a routine with the same name as an existing routine, future calls use the new routine. Prior versions of that routine referenced by the stack remain tied to the stack until they QUIT, at which point they become inaccessible. This provides a mechanism to patch long-running processes. If gtm_link is undefined or set to NORECURSIVE, or any value other than "RECURSIVE", auto-zlink defers replacing older routines until they no longer have an invoking use by the process and a ZLINK command produces a LOADRUNNING error when it attempts to relink an active routine on the GT.M invocation stack.

gtm_local_collate specifies an alternative collation sequence for local variables.

gtm_linktmpdir provides a location into GT.M creates small temporary files used for auto-relink; if unspecified, this location defaults to $gtm_tmp, which in turn defaults to /tmp. The implications for group and permissions of the directory are described in the section Shared Resources Authorization Permissions of Appendix D: “GT.M Security Philosophy”. FIS recommends that all processes that share a directory whose contents are subject to ZRUPDATE use the same value for $gtm_linktmpdir so that all processes see update notifications - with different values of $gtm_linktmpdir, a ZRUPDATE by a process with one value of $gtm_linktmpdir would not be observed by a process with a different value of that environment variable.

gtm_max_indrcache_count (use only under the guidance of your GT.M support channel) specifies the number of cached entries in indirection compilation. The default is 128.

gtm_malloc_limit specifies an initial value for $ZMALLOCLIM. The default is 0, which indicates no warning limit on process memory utilization. When the environment variable specifies a positive value, GT.M uses the smaller of that value and any OS defined amount for the value of $ZMALLOCLIM. GT.M does not give errors or messages about its choice for $ZMALLOCLIM between a specified value and some other more appropriate value, so if the application needs to verify the result, it should examine the resulting ISV value For additional information, refer to the $ZMALLOCLIM section in the Intinsic Special Variable chapter of the GT.M Programmer's Guide.

gtm_max_indrcache_memory (use only under the guidance of your GT.M support channel) specifies the maximum size (in KiB) of memory that GT.M should use for indirection cache object code. The default is 128.

gtm_max_sockets specifies the maximum number of client connections for socket devices. The default is 64.While it must be large enough to accommodate the actual need, each reservation requires some memory in socket structures, so setting this number unnecessarily high causes requires a bit of additional memory for no benefit.

gtm_memory_reserve specifies the size in kilobytes of the reserve memory that GT.M should use in handling and reporting an out-of-memory condition. The default is 64 (KiB). Setting this too low can impede investigations of memory issues, but GT.M only uses this reserve when a process runs out of memory so it almost never requires actual memory, only address space.

gtm_mstack_crit_threshold specifies an integer between 15 and 95 defining the percentage of the stack which should be used before GT.M emits a STACKCRIT warning. If the value is below the minimum or above the maximum GT.M uses the minimum or maximum respectively. The default is 90. Note that if a single application call generates a stack frame larger than the space between the STACKCRIT and STACKOFLOW boundaries, the process puts a STACKCRIT message in the operator log, but processes the STACKOFLOW and terminates, so the application gets no chance to intervene and handle the error.

gtm_mstack_size specifies the M stack size (in KiB). If gtm_mstack_size is not set or set to 0, GT.M uses the default M stack size (that is, 272KiB). The minimum supported size is 25 KiB; GT.M reverts values smaller than this to 25 KiB. The maximum supported size is 10000 KiB; GT.M reverts values larger than this to 10000 KiB.

gtm_mupjnl_parallel defines the number of processes or threads used by MUPIP JOURNAL -RECOVER/-ROLLBACK when the invoking command does not have a -PARALLEL qualifier. When defined with no value, it specifies one process or thread per region. When undefined or defined to one (1), it specifies MUPIP should process all regions without using additional processes or threads. When defined with an integer value greater than one (1), it specifies the maximum number of processes or threads for MUPIP to use. If the value is greater than the number of regions, MUPIP never uses more processes or threads than there are regions. If it is less than the number of regions, MUPIP allocates work to the additional processes or threads based on the time stamps in the journal files.

gtm_nocenable specifies whether the $principal terminal device should ignore <CTRL-C> or use <CTRL-C> as a signal to place the process into direct mode; a USE command can modify this device characteristic. If gtm_nocenable is defined and evaluates to a non-zero integer or any case-independent string or leading substrings of "TRUE" or "YES", $principal ignores <CTRL-C>. If gtm_nocenable is not set or evaluates to a value other than a positive integer or any case-independent string or leading substrings of "FALSE" or "NO", <CTRL-C> on $principal places the process into direct mode at the next opportunity (usually at a point corresponding to the beginning of the next source line).

gtm_non_blocked_write_retries modifies the write behavior of FIFO, PIPE, or non-blocking sockets. GT.M retries a WRITE which would block up to $gtm_non_blocked_retries times with a 100 milliseconds delay between each retry. The default value is 10 times.

gtm_nontprestart_log_delta specifies the number of non-transaction restarts for which GT.M should wait before reporting a non-transaction restart to the operator logging facility. If gtm_nontprestart_log_delta is not defined, GT.M initializes gtm_nontprestart_log_delta to 0.

gtm_nontprestart_log_first specifies the initial number of non-transaction restarts which GT.M should report before placing non-transaction restart reports to the operator logging facility using the gtm_nontprestart_log_delta value. If gtm_nontprestart_log_delta is defined and gtm_nontprestart_log_first is not defined, GT.M initializes gtm_nontprestart_log_first to 1.

gtm_noundef specifies the initial setting that controls whether a GT.M process should treat undefined global or local variables as having an implicit value of an empty string. If it is defined, and evaluates to a non-zero integer or any case-independent string or leading substring of "TRUE" or "YES", then GT.M treats undefined variables as having an implicit value of an empty string. The VIEW "[NO]UNDEF" command can alter this behavior in an active process. By default, GT.M signals an error on an attempt to use the value of an undefined variable.

gtm_obfuscation_key: If $gtm_obfuscation_key specifies the name of file readable by the process, the encryption reference plugin uses a cryptographic hash of the file's contents as the mask for the obfuscated password in the environment variable gtm_passwd. When gtm_obfuscation_key does not point to a readable file, the plugin computes a cryptographic hash using a mask based on the value of $USER and the inode of the mumps executable to use as a mask. $gtm_passwd set with a $gtm_obfuscation_key allows access to all users who have the same $gtm_obfuscation_key defined in their environments. However, $gtm_passwd set without $gtm_obfuscation_key can be used only by the same $USER using the same GT.M distribution.

gtm_passwd specifies the obfuscated (not encrypted) password of the GNU Privacy Guard key ring. When the environment variable $gtm_passwd is set to "", GT.M invokes the default GTMCRYPT passphrase prompt to obtain a passphrase at process startup and uses that value as $gtm_passwd for the duration of the process.

gtm_patnumeric specifies the value of the read-only ISV $ZPATNUMERIC that determines how GT.M interprets the patcode "N" used in the pattern match operator. The SET command can alter the value of $ZPATNUMERIC in an active process. If the environment variable gtm_patnumeric is not defined or set to a value other than "UTF-8", GT.M initializes $ZPATNUMERIC to "M".

gtm_pattern_file and gtm_pattern_table specify alternative patterns for the pattern (?) syntax. Refer to the Internationalization chapter in the Programmer's Guide for additional information.

gtm_pinshm specifies the initial setting that controls whether a GT.M process should attempt to pin shared memory into physical memory. If it is defined and evaluates to a non-zero integer or any case-independent string or leading substring of "TRUE" or "YES" in a GT.M process creating shared memory, GT.M attempts to pin such memory used for database global buffers, replication buffers, and routine buffers into physical memory. Huge pages are implicitly locked in physical memory, so GT.M does not attempt to pin shared memory buffers backed by huge pages. $gtm_pinshm does not pin memory used by online INTEG (integchk snapshot). Pinning may not succeed due to insufficient physical memory and/or OS configuration. By default, GT.M does not attempt to pin shared memory.

gtm_poollimit restricts the number of global buffers used by a mumps or a reorg process to up to 50% of the total number of the configured global buffers. The value of $gtm_poollimit is of the form n[%]. When $gtm_poollimit ends with a percent sign (%), the value is taken as a percentage of the configured global buffers.

With mumps processes, $gtm_poollimit sets threshold at which processes start flushing dirty buffers. When $gtm_poollimit is not set, the database settings for global buffers apply. GT.M MUMPS processes can use VIEW "POOLLIMIT":REGION:n[%] to programmatically restrict their use of global buffers.

For a reorg process, gtm_poollimit applies this restriction at the block level use of global buffers. If gtm_poollimit is not defined, the limit is 64 global buffers. This setting does not restrict the global buffer use when reorg writes before image records.

gtm_principal specifies the value for $PRINCIPAL, which designates an alternative name (synonym) for the principal $IO device.

gtm_principal_editing specifies the initial settings for $PRINCIPAL of the following colon-delimited deviceparameters: [NO]EDITING [NO]EMPTERM and [NO]INSERT; in an active process the USE command can modify these device characteristics.

gtm_procstuckexec specifies a shell command or a script to execute when any of the following conditions occur:

You can use this as a monitoring facility for processes holding a resource for an unexpected amount of time. Typically, for the shell script or command pointed to by gtm_procstuckexec, you would write corrective actions or obtain the stack trace of the troublesome processes (using their PIDs). GT.M passes arguments to the shell command / script in the order specified as follows:

Each invocation generates an operator log message and if the invocation fails an error message to the operator log. The shell script should start with a line beginning with #! that designates the shell.

gtm_prompt specifies the initial value of the ISV $ZPROMPT, which controls the GT.M direct mode prompt. The SET command can alter the value of $ZPROMPT in an active process.By default, the direct mode prompt is "GTM>".

gtm_quiet_halt specifies whether GT.M should disable the FORCEDHALT message when the process is stopped via MUPIP STOP or by a SIGTERM signal (as sent by some web servers).

gtm_repl_instance specifies the location of the replication instance file when database replication is in use.

gtm_repl_instname specifies a replication instance name that uniquely identifies an instance. The replication instance name is immutable. The maximum length of a replication instance name is 15 bytes. Note that the instance name is not the same as the name of the replication instance file (gtm_repl_instance). You need to specify a replication instance name at the time of creating an replication instance file. If you do not define gtm_repl_instname, you need to specify an instance name using -NAME=<instance_name> with MUPIP REPLICATE -INSTANCE_CREATE.

gtm_repl_instsecondary specifies the name of the replicating instance in the current environment. GT.M uses $gtm_repl_instsecondary if the -instsecondary qualifer is not specified.

gtm_retention (used by the gtm/gtmprofile script) - On every invocation, the gtm script deletes all prior generation journal files (*_<time and date stamp>) older than $gtm_retention days from the directory (and its subdirectories) of the global directory. By default, $gtm_retention is 42.

gtm_side_effects: When the environment variable gtm_side_effects is set to one (1) at process startup, GT.M generates code that performs left to right evaluation of actuallist arguments, function arguments, operands for non-Boolean binary operators, SET arguments where the target destination is an indirect subscripted glvn, and variable subscripts. When the environment variable is not set, or set to zero (0), GT.M retains its traditional behavior, which re-orders the evaluation of operands using rules intended to improve computational efficiency. This reordering assumes that functions have no side effects, and may generate unexpected behavior (x+$increment(x) is a pathological example). When gtm_side_effects is set to two (2), GT.M generates code with the left-to-right behavior, and also generates SIDEEFFECTEVAL warning messages for each construct that potentially generates different results depending on the order of evaluation. As extrinsic functions and external calls are opaque to the compiler at the point of their invocation, it cannot statically determine whether there is a real interaction. Therefore SIDEEFFECTEVAL warnings may be much more frequent than actual side effect interactions and the warning mode may be most useful as a diagnostic tool to investigate problematic or unexpected behavior in targeted code rather than for an audit of an entire application. Note that a string of concatenations in the same expression may generate more warnings than the code warrants. Other values of the environment variable are reserved for potential future use by FIS. It is important to note that gtm_side_effects affects the generated code, and must be in effect when code is compiled - the value when that compiled code is executed is irrelevant. Note also that XECUTE and auto-ZLINK, explicit ZLINK and ZCOMPILE all perform run-time compilation subject to the characteristic selected when the process started. Please be aware that programming style where one term of an expression changes a prior term in the same expression is an unsafe programming practice. The environment variable gtm_boolean may separately control short-circuit evaluation of Boolean expressions but a setting of 1 (or 2) for gtm_side_effects causes the same boolean evaluations as setting gtm_boolean to 1 (or 2). Note that warning reports for the two features are separately controlled by setting their values to 2. The differences in the compilation modes may include not only differences in results, but differences in flow of control when the code relies on side effect behavior.

gtm_snaptmpdir specifies the location to place the temporary "snapshot" file created by facilities such as MUPIP INTEG -ONLINE. If $gtm_snaptmpdir is not defined, GT.M currently uses the deprecated $GTM_BAKTMPDIR environment variable. If $GTM_BAKTMPDIR is not defined, MUPIP INTEG uses the current working directory. For the INTEG to succeed, all processes performing updates during an MUPIP INTEG -ONLINE must use the same snapshot directory and have effective write access.

gtm_statsdir specifies the directory for database files into which processes opted-in to sharing global statistics place their statistics as binary data. If you do not explicitly define this environment variable for a process, GT.M defines this to the evaluation of $gtm_tmp, which defaults to /tmp. All processes that share statistics MUST use the same value for $gtm_statsdir. FIS suggests that you point gtm_statsdir at a tmpfs or ramfs on Linux, and a filesystem in a ram disk on AIX. These database files have a name derived from the user defined database file name and a .gst extension. They are not usable as normal database files by application code, except to read statistics. GT.M automatically creates and deletes these database files as needed. Under normal operation, applications do not need to manage them explicitly. The mapping of ^%YGS to statistics database files is managed by GT.M within global directories, transparently to applications. The ^%YGBLSTAT utility program gathers and reports statistics from nodes of ^%YGS(region,pid).

gtm_statshare specifies an initial value for the characteristic controlled by VIEW "[NO]STATSHARE" in application code. A value of 1, or any case-independent string or leading substrings of "TRUE" or "YES" in the environment variable gtm_statshare provides the equivalent of VIEW "STATSHARE" (without the region-list) as the initial value when a database file is opened. Leaving the gtm_statshare undefined or defined to another value, typically 0, "FALSE" or "NO" provides the equivalent of VIEW "NOSTATSHARE" (without the region-list) as the initial value.

gtm_stdxkill enables the standard-compliant behavior to kill local variables in the exclusion list if they had an alias that as not in the exclusion list. By default, this behavior is disabled.

gtm_string_pool_limit when positive, specifies the initial value in bytes for $ZSTRPLLIM.

gtm_sysid specifies the value for the second piece of the $SYstem ISV. $SYSTEM contains a string that identifies the executing M in stance. The value of $SYSTEM is a string that starts with a unique numeric code that identifies the manufacturer . Codes were originally assigned by the MDC (MUMPS Development Committee). $SYSTEM in GT.M starts with "47" followed by a comma and $gtm_sysid.

gtm_tmp specifies a directory where GT.M stores socket files for communication between gtmsecshr and GT.M processes. FIS recommends setting the environment variable gtm_tmp to a location:

If appropriate, set gtm_tmp to a directory location in tmpfs or ramfs on Linux or a filesystem in a ram disk on AIX.

If gtm_tmp is not defined, GT.M uses the /tmp directory which may disrupt active gtmsecshr operations when /tmp is either cleared manually or by the retention policies of the operating system.

gtm_tpnotacidtime specifies the maximum time that a GT.M process waits for non-Isolated or timed command (HANG, JOB, LOCK, OPEN, READ, WRITE /*, ZALLOCATE, ZEDIT or external call) running within a transaction to complete before it releases all critical sections it owns and sends a TPNOTACID information message to the system log. A GT.M process owns critical sections on all or some of the regions participating in a transaction only during database critical section holding retry attempts (when $TRETRY>2). gtm_tpnotacidtime specifies time in seconds to millisecond precision (three decimal places); the default is 2 seconds. The maximum value of gtm_tpnotacidtime is 30 and the minimum is 0. If gtm_tpnotacidtime specifies a time outside of this range, GT.M uses the default value. The GT.M behavior of releasing critical sections in critical section holding retry attempts to provide protection from certain risky coding patterns which, because they are not Isolated, can cause deadlocks (in the worst case) and long hangs (in the best case). As ZSYSTEM and BREAK are neither isolated nor timed, GT.M initiates TPNOTACID behavior for them immediately as it encounters them during execution in a critical section holding attempt (independent of gtm_tpnotacidtime). Rapidly repeating TPNOTACID messages are likely associated with live-lock, which means that a process is consuming critical resources repeatedly within a transaction, and is unable to commit because the transaction duration is too long to commit while maintaining ACID transaction properties.

gtm_tpnotacidtries specifies the limit between four (4) and 100, or a special value of zero (0) of retries after which GT.M issues a trappable TPNOTACID error in order to limit livelock. The default value is 16. Specifying a value outside the supported values silently reverts to the default. The setting of zero (0) acts like an audit by reporting all encountered operations capable of causing TPNOTACID detection to the syslog but setting the actual error limit to the default .

gtm_tprestart_log_delta specifies the number of transaction restarts for which GT.M should wait before reporting a transaction restart to the operator logging facility. If gtm_tprestart_log_delta is not defined, GT.M initializes gtm_tp_restart_log_delta to 0.

gtm_tprestart_log_first specifies the initial number of transaction restarts which GT.M should report before pacing transaction restart reports to the operator logging facility using the gtm_tprestart_log_delta value. If gtm_tprestart_log_delta is defined and gtm_tprestart_log_first is not defined, GT.M initializes gtm_tprestart_log_first to 0.

gtm_trace_gbl_name enables GT.M tracing at process startup. Setting gtm_trace_gbl_name to a valid global variable name instructs GT.M to report the data in the specified global when a VIEW command disables the tracing, or implicitly at process termination. This setting behaves as if the process issued a VIEW "TRACE" command at process startup. However, gtm_trace_gbl_name has a capability not available with the VIEW command, such that if the environment variable is defined but evaluates to zero (0) or to the empty string, GT.M collects the M-profiling data in memory and discards it when the process terminates (this feature is mainly used for in-house testing). Note that having this feature activated for processes that otherwise don't open a database file (such as GDE) can cause them to encounter an error.

gtm_trigger_etrap provides the initial value for $ETRAP in trigger context; can be used to set trigger error traps for trigger operations in both mumps and MUPIP processes.

gtm_zdate_form specifies the initial value for the $ZDATE ISV. The SET command can alter the value of $ZDATE in an active process.

gtm_zinterrupt specifies the initial value of the ISV $ZINTERRUPT which holds the code that GT.M executes (as if it is the argument for an XECUTE command) when a process receives a signal from a MUPIP INTRPT command. The SET command can alter the value of $ZINTERRUPT in an active process.

gtm_zlib_cmp_level specifies the zlib compression level used in the replication stream by the source and receiver servers. By default, replication does not use compression.

gtm_zmaxtptime specifies the initial value of the $ZMAXTPTIME Intrinsic Special Variable, which controls whether and when GT.M issues a TPTIMEOUT error for a TP transaction that runs too long. gtm_zmaxtptime specifies time in seconds with millisecond precision and the default is 0, which indicates "no timeout" (unlimited time). GT.M ignores gtm_zmaxtptime if it contains a negative.

gtm_zquit_anyway specifies whether the code of the form QUIT <expr> execute as if it were SET <tmp>=<expr> QUIT:$QUIT tmp QUIT, where <tmp> is a temporary local variable in the GT.M runtime system that is not visible to application code. This setting is a run-time setting, rather than a compiler-time setting. If gtm_zquit_anyway is defined and evaluates to 1 or any case-independent string or leading substrings of "TRUE" or "YES", code of the form QUIT <expr> executes as if it were SET <tmp>=<expr> QUIT:$QUIT tmp QUIT. If gtm_zquit_anyway is not defined or evaluates to 0 or any case-independent string or leading substrings of "FALSE" or "NO", GT.M executes QUIT <expr> as specified by the standard..

gtm_zstep specifies the initial value of $ZSTEP, which defines the ZSTEP action; if gtm_zstep is not defined, $ZSTEP defaults to "B".

gtm_ztrap_form and gtm_zyerror specify the behavior of error handling specified by $ZTRAP as described in the Error Processing chapter of the GT.M Programmer's Guide.

gtm_ztrap_new specifies whether a SET $ZTRAP also implicitly performs a NEW $ZTRAP before the SET.

The gtmprofile and gtmschrc scripts sets the following environment variables. FIS recommends using the gtmprofile script (or the gtm script which sources gtmprofile) to set up an environment for GT.M.

While creating an environment for multiple processes accessing the same version of GT.M, bear in mind the following important points:

Always set the same value of $gtm_tmp for all processes using the same GT.M version. Having different $gtm_tmp for multiple processes accessing the same GT.M version may prevent processes from being able to communicate with gtmsecshr and cause performance issues.