This topic lists environment variables relate to configuring the IMS environment.
- Specifies the locations of the IMS ACB files.
pathname The path location of the IMS ACB files.
If this variable is not set the ACB files are assumed to be in the project directory.
The default transaction to execute or MOD file to be displayed after successfully signing on to IMS. You specify these by
setting environment variables prior to the start of the region: ES_DFS3650 - set to MOD if a MOD file is to be sent, or TRX
if a TRANSACTION is to be executed. If you set to MOD, ES_MOD3650 needs to be set to the name of the MOD you want to display.
If you set to TRX, ES_TRX3650 needs to be set to the name of the transaction.
- MOD - ES_MOD3650 needs to be set to the name of the MOD you want to display
- TRX - ES_TRX3650 needs to be set to the name of the transaction
- No default transaction or MOD.
- When set to 1, enables a basic checkpoint call to process as if a SYNC call had been issued. The default is 0 (zero).
- By default, a CHNG call issued from an OTMA- or IMS Connect-submitted transaction assumes that the destination is the OTMA
client. In some circumstances, the previous behavior of assuming a non-OTMA client is desirable. To use the previous behavior,
set this environment variable to Y.
- Controls the caching of IMS binaries.
Permissible values for
- P - Performs a physical cancel; every transaction will have new-copy behavior. This option is the default behavior, but is
the poorest performing of the options.
- L - Performs a logical cancel. This gives the best performance of the options, but can only be used it there is only one DLITCBL
entry point in an MPR.
- D - Performs a deferred cancel, which will yield the same behavior as a logical cancel when the MPR services the same MPP
back-to-back. It will behave as P (physical cancel) when the transaction changes.
- By default, an IMS Connect request sets LTERM (if not explicitly overridden) to the client-ID when commit-mode is zero and
port-ID when commit-mode is one. Setting this variable to "Y" overrides this behavior to have LTERM be set to the client-ID
instead of the port-ID.
- The IMS TM parameters.
- When set to 0 (zero), forces the flushing of database buffers to disk on CLOSE only (default). When set to 1, forces the
flushing of database buffers to disk on COMMIT only.
- When set to 0 (zero), forces the flushing of TLOG buffers to disk on COMMIT only (default). When set to 1, forces the flushing
of TLOG buffers to disk on all database I/O.
- Time in milliseconds to wait before checking for a deadlock. The default is 1000 (1 second).
- Marks IMS TM as diagnose mode only for IMSMSGQ.
When set to Y, the Transaction Manager (TM) works in diagnostic mode only, and no activity key points are written to the message
Set ES_IMS_DIAGNOSE only when advised to do so by
- Emulates DOS/VSE PCB address alignment for EXEC DLI programs.
- Creates a system dump when a deadlock is detected.
- Creates a system dump when a lock timeout occurs.
- The location of compiled code that contains segment, field, and/or print exits.
- Enables a user to force a sign-on to IMS on the current terminal and sign off from other terminals.
- Returns to CICS upon logging off or timing out, rather than returning to the IMS sign-on screen, which is the default behavior.
- Sets the emulation for the IMS run-time. Valid values are: M (for MVS) or D (for DOSVS). The default value is M.
Note: This variable is rarely required to be changed from its default, even for the majority of DOSVS users.
- Allows the user to specify the IMS System ID returned to the AIBTDLI INQY ENVIRON call.
- Returns TPIPE, MBR, SYNC, and MSYNC to an INQY call.
- Value returned to an INQY call.
- Enables Internal Lock Resource Manager (IRLM) locking. IRLM locking more closely parallels mainframe IMS database DB locking
behavior, reducing data constraint and potential for deadlock.
- The default setting is Y. IMS marks a JES container as dirty if an IMS application abends or is aborted. To disable this behavior,
set this environment variable to N:
- Deprecated. See
IMS Database Locking. When set to 1, directs batch program execution to process all IMS DB calls entirely in the JES initiator providing significant
performance improvement. All IMS DB control processes accessed from the batch program must be stopped before execution because
they become exclusively owned by JES until the program completes.
- The IMS DB lock retry delay in milliseconds.
The number of seconds during which IMS DB control continues to retry a locked record before timing out. Valid values are 0
to 65535. The default is 30 seconds; a value of 0 indicates an indefinite wait time.
- Specify a one- to four-character LTERM prefix alternative to the default (OTMA) to use when the ES_IMS_SINGLE environment
variable is set to
N. Use of an alternative prefix to OTMA enables you to exercise control over name conflicts.
Use up to four characters of your choice.
Enterprise Server pads the value specified with numeric digits up to eight characters, enabling the LTERM pool to be expanded from 9999 up
to 999999. The pool size is dictated by the number of characters used in the specified prefix. For example, the LTERM pool
size for a four-character prefix is 9999; for a three-character prefix is 99999; and so on.
Note: The default setting of this environment variable suggests that the LTERMS apply only to OTMA clients; however, this is not
the case. LTERMS can also be applied to second and subsequent 3270 user connections.
- Determines the value of the LTERM literal returned by the MFS system. Valid values are: Y to return the LU name; N to return
the user ID.
- Sets the configuration for the IMS TM message queue. The ES_IMS_MESGQ environment variable is generated and set automatically
Enterprise Server, and is reserved.
Restriction: Manually set this variable only when advised to do so by
- An alternative data store file to the default, which is
- Data store size limit represented as the number of 64K blocks. Default is
- The number of 64K buffers to allocate. Default is
- A flag that sets the start behavior as follows:
| Cold start the resource definitions. Default.
| Cold start the statistics and resource state information.
| Cold start the data store (system cold start).
- The size of the cushion to be reserved for graceful lack-of-space behavior, represented as a number from 0 to 255. The specified
number represents 32 times the actual percentage of
max-blocks reserved for emergency use. The default is
4 (a raw value of 128).
- Defines the wait period in seconds during which IMS retries the opening of a database file that is in use by another task.
Default is 30 seconds.
- Each specified destination consists of the destination name, the NONOTMA keyword, and the LU type (LU1 or LU3) separated by
commas. Each destination definition is separated by a semi-colon.
- The location of compiled COBOL applications.
Determines whether the PL/I program converts the PCB address list from a direct to an indirect addressing technique. Set the
variable to one of the following values:
- If the main program is a PL/I program, PCB addresses are converted from a direct to an indirect addressing technique.
- Always converts addresses from a direct to an indirect addressing technique as long as the PSB language is set to PL/I.
- Never converts addresses from a direct to an indirect addressing technique.
The default is D (dynamic).
Creates a set of newly-named IMS security resource classes, appending the variable's value (maximum of seven characters)
to each resource class' default character.
Create theses custom-named classes if you are using the same ESM active directory with two Enterprise Server systems and
your security needs to differ for each.
Resource Classes for IMS Security for the names of the resource classes created if this variable is not set.
- Allows the user to specify the IMS Release returned to the AIBTDLI INQY ENVIRON call.
- Allows the user to specify the IMS Region returned to the AIBTDLI INQY ENVIRON call.
- Enables automatic Backward Recovery; enabled by default.
- Enables or disables Forward Recovery logging. Valid values are: Y to enable; N to disable. The default is N.
- Enables or disables functionality that allows a single user to sign on to multiple LUs simultaneously.
- Disables multiple sign-on functionality.
- Enables multiple sign-on functionality.
When ES_IMS_SINGLE is set to N, and a user attempts to sign on to an LU using a sign-on that is currently active at another
LU, IMS Transaction Manager (TM) assigns a temporary LTERM to the user and LU using a name constructed from the ES_IMS_LTERM_PREFIX
setting followed by a numerical value totalling eight characters (see the
IMS_LTERM_PREFIX entry in this topic for details). The temporary LTERM is the destination for the user and LU irrespective of activity at
other LUs controlled by the user. When a user disconnects from an LU that is served by a temporary LTERM, the LTERM is returned
to the temporary pool for reuse.
Also when ES_IMS_SINGLE is set to N, the execution of
/dis USER all returns a sub-list for each user that shows all active connections. These connections persist throughout a session, and are
dynamically recreated during a warm start.
Note: No KEYPOINT activity is associated with the use of ES_IMS_SINGLE.
Indicates the language of the IMS DB secondary index sparse routines.
C (for COBOL)
A (for Assembler)
By default, this variable is not set (sparse exits are disabled).
- Enables IMS support.
- When set to 0 (zero), disables compression of the Backward Recovery TLOG file. When not compressed, the file contains only
the information required to recover databases. The default is enabled.
Note: When enabled,
Enterprise Server reclaims space in the file when information becomes obsolete.
- When set to 1, forces the frequent flushing of TLOG and database buffers to disk.
Warning: Depending upon the number of database updates, the frequency of commits, and other computer activity, use of ES_IMS_TLOG_FLUSH
could result in significant performance degradation.
Note: This environment variable is deprecated. Use ES_IMS_DB_TLOG_WRITETHRU to flush TLOG buffers and ES_IMS_DB_COMMIT_FLUSH to
flush database buffers.
- Maximum size of the IMS DB transaction logging file in bytes. The default is 4GB or h"FFF00000".
- The location of IMS DB transaction logging files. The default is the
Enterprise Server system directory.
Note: Once created, you can move log files, but do not rename them. Before attempting to recover a database, all log files must
reside in the directory specified by ES_IMS_TLOG_PATH.
- Threshold size of the IMS DB transaction logging file. When reached, the current TLOG file is closed and a new TLOG file
created for subsequent transactions. The default is 2GB or h"7FFFFFFF".
- The location of the IMS configuration files
- The location of IMS DB data files.
- The location of
- The location of the control blocks generated by the MFS generation program.
pathname The path to the MFS directory.
- The default MOD file to be displayed after a successful sign-on to IMS.
- filename - The name of the MOD file.
- Location of the JCL used to initialize the SSTM IMS environment.
- Controls the performance environment for IMS TM data stores. See
Environment variables in alphabetical order for details.
- Sets the default behavior, which is to unilaterally flush operating system buffers to your physical disk at each key transactional
point. While this does not change the method used by default at startup, it does enable dynamic modification via ESMAC. Once
set, you can then test the effect of various non-default settings by altering them dynamically.
- Disables the transactional flushing of operating system buffers to disk. This option can significantly enhance message queue
performance; however it is at the expense of the transactional integrity of the message queue in the event of a system failure.
To avoid unpredictable results when using this setting, we highly recommend that you also set the static options as follows
on the Administration
Server > Properties > MSS > IMS > TM > General
Cold start to
Server Instance Properties: MSS IMS TM General
- Enables the aggregated transactional flushing of operating system buffers to disk where
nnn represents an interval of time, in milliseconds, during which additional buffers are allowed to accumulate before flushing.
Valid values are
Once a thread reaches a key transactional point and requests a flush, TM waits the specified interval to accumulate subsequent
threads that also request a flush. At the end of the interval, one flush is performed for all accumulated requests thus potentially
improving performance by reducing the number of flush commands issued to the operating system.
- Threads requesting a flush wait until the flush is confirmed.
- Generally, when the message queue resides on a higher performance I/O subsystem such as one using SSDs, a smaller value,
2, produces the best results. A value of
10 or higher seldom improves performance.
- The default transaction to run after a successful sign-on to IMS.
- transaction The default transaction to run.
- Allows you to override the default user when no user is logged on for IMS authentication.
user - The user name to override the default.
- Controls the client TCP connection status of an IMS Connect emulator.
- The location of copybook files for DBDGEN, PSBGEN and MFSGEN utilities .
- Suppresses date/time stamp display in ACB report.
- Returns a QC to a checkpoint call when it the call includes an IO area.
- Configures Mainframe Express-format BTS tracing
- Specifies additional DIBSTAT return codes to be returned to EXEC DLI program.
- Specifies DL/I call optimization flags.
- Enables IMS BTS format diagnostic tracing.
- Flushes BTS trace file to disk after every write.
- Bypasses keycheck on IMS Fastpath DB delete.
- Disables load of MVS support for IMS application programs.
- Allows a standalone EXEC DLI program to issue a PCB call.