FASTPATH section of the DFSDFxxx member

Parameters

ACBSHR=

Specifies whether the ACB libraries are shared among the IMS systems when the DEDB Alter Utility runs. This parameter can be specified in both the DFSCGxxx and DFSDFxxx members of the IMS PROCLIB data set. If it is specified in both members, IMS uses the ACBSHR value that is specified in the DFSCGxxx member of the IMS PROCLIB data set.

Y

Specifies that all the IMS systems use the same ACB library.

N

Specifies that each IMS uses its own dedicated ACB library.

Each IMS system must have the same value for ACBSHR=. If the ACBSHR= values are not the same, the DEDB Alter utility terminates without performing the requested function.

You can also specify ACBSHR in the COMMON_SERVICE_LAYER section of the DFSDFxxx member. When this parameter is used multiple times, the following describes the order of preference for ACBSHR=Y|N value:

1. DFSCGxxx PROCLIB member: ACBSHR=Y|N value
2. DFSDFxxx PROCLIB member <SECTION=COMMON_SERVICE_LAYER>: ACBSHR=Y|N value
3. Default ACBSHR=Y for Common Service Layer if ACBSHR=Y|N not specified in 1st and 2nd.
4. DFSDFxxx PROCLIB member <SECTION=FASTPATH>: ACBSHR=Y|N value
5. Default ACBSHR=Y for <SECTION=FASTPATH> if not specified in 4th.

ALTERGRP=

Specifies the 1- to 5-character alphanumeric name for the DEDB Alter data-sharing group. If an IMS is to participate in a DEDB Alter process, ALTERGRP= must be specified in the DFSDFxxx PROCLIB member for each data sharing IMS system.

ALTERGRP= contains 1 - 5 alphanumeric characters that are prefixed by DBF. The DEDB Alter data sharing group that data sharing IMS systems join is DBFxxxxx. There is no default value for ALTERGRP=xxxxx.

ALTERHLQ=

Specifies the 1- to 8-character alphanumeric name for the high-level qualifier of temporary data sets for the DEDB Alter utility. ALTERHLQ=DBFUDAWK is the default.

BYPASS_EXTENT=N | Y

In IMS 15, a bypass extent check enhancement for DEDB data sets is added to the available Fast Path options. When enabled, this enhancement specifies that normal extent checking will be suspended while data is being written.

Enabling this option could result in improved performance in certain cases when multiple applications are simultaneously reading or writing the same disk extent ranges. For example, users of HSSP or HSRE with a Metro Mirror configuration may benefit from use of this feature.

Normally, when your program writes on DASD, the DASD subsystem performs extent serialization that prevents all access to that extent from all other programs on all systems while data is being written. This prevents other programs from reading and writing within the extent and from seeing certain types of incomplete updates. But if bypass extent check is enabled by coding BYPASS_EXTENT=Y in the FASTPATH section of the DFSDFxxx member, the DASD subsystem will serialize access to only one track at a time, not to the whole extent.

If you know that other programs might be reading the data set at the same time that your program is writing and that a mechanism exists within those other programs to avoid or tolerate potentially incomplete updates within an extent, then enabling bypass extent check could provide improved performance due to normal extent serialization being suspended.

It is acceptable to have bypass extent check enabled on one IMS and disabled on the other(s), but the bypass extent check option will not become active until it is enabled on all systems.

When enabled, bypass extent check will function for all supported DEDB CI sizes except for:

• 3380 DASD: 12 KB, 16 KB, 24 KB, and 28 KB
• 3390 DASD: 20 KB and 28 KB

N

Specifies that bypass extent check is not enabled. When IMS starts, message DFS1919I is displayed for BYPASS_EXTENT = N in the DFSDF member. This is the default.

Y

Specifies that bypass extent check is enabled. When IMS starts, message DFS1919I is displayed for BYPASS_EXTENT = Y in the DFSDF member.

DEDBGT2K=N | Y

Y

Specifies that this IMS opens more than 2048 areas under one DEDB. When IMS starts, message DFS1929I is displayed for DEDBGT2K in the DFSDF member or the default value of DEDBGT2K=N.

N

Specifies that this IMS does not open more than 2048 areas under one DEDB. This is the default.

DEF_NBA=

Specifies the default NBA number to override the NBA= parameter of a BMP procedure. A valid range is 0 - 9999. This value is valid only when FPBP64=Y is specified. If FPBP64=N, then the DFS4787I message is issued. When an invalid value is specified, BPE0003E shows the invalid value and the default value 0 is set in DEF_NBA. In this case, you need to specify a valid value, and you must restart IMS or specify the values for NBA= and OBA= to the BMP procedure.

DEF_OBA=

Specifies the default OBA number to override the OBA= parameter of a BMP procedure. A valid range is 0 - 9999. This value is valid only when FPBP64=Y is specified. If FPBP64=N, then the DFS4787I message is issued. When an invalid value is specified, BPE0003E shows the invalid value, and the default value 0 is set in DEF_OBA. In this case, you must specify a valid value, and you must restart IMS or specify values for NBA= and OBA= to the BMP procedure.

FPBP64=N | Y

Specifies whether to enable the Fast Path 64-bit buffer manager. If you choose to use the Fast Path 64-bit buffer manager (FPBP64=Y), the DBBF, DBFX, and BSIZ parameters that define Fast Path buffers are ignored. If you specify FPBP64=N, Fast Path buffer management is defined by the DBBF, DBFX, and BSIZ parameters on the startup procedure. FPBP64=N is the default.

If Fast Database Recovery (FDBR) is being used, and the Fast Path 64-bit buffer manager is enabled, you must specify the DFSDF= parameter to reference this DFSDFxxx member on the FDR procedure. This action ensures that the same Fast Path 64-bit buffer manager is used by both IMS and FDBR.

Important: If you change the FASTPATH section of the DFSDFxxx member, you must perform a cold start of the system. If you perform a normal start instead, message DFS0168I RSN=1B and ABENDU0168 are issued. The FPSISETI parameter may be changed with a warm start.

FPBP64M=

Use this parameter to set a maximum limit on how much 64-bit storage the Fast Path 64-bit buffer pool uses for DEDB data buffers. If FPBP64=Y is specified, this parameter is required. If FPBP64=Y is not specified, FPBP64M is ignored.

The value is specified as a decimal value, in bytes, kilobytes, or megabytes, where:

xxxxx

Bytes. Maximum value is 2147483647.

xxxxxK

Kilobytes. Maximum value is 2097151K.

xxxxxM

Megabytes. Maximum value is 2047M.

The valid range is 1M - 2047M. The minimum value for this parameter is the amount of 64-bit storage that is initially allocated for the subpools (without any extents).

Once the specified limit is exceeded, it disallows the schedule of new threads. Currently, active threads are unaffected and can force the limit past the threshold that is established by FPBP64M. In other words, if the amount of required 64-bit storage is greater than the value specified for FPBP64M, FPBP64M is increased and a DFS3299I message is issued.

The value for this parameter can be updated with the UPDATE POOL TYPE(FPBP64) SET(LIMIT(xxxxx)) command.

FPBP64C=N | Y

Specifies whether the Fast Path 64-bit buffer manager releases buffer storage when the number of buffers is reduced. FPBP64C=N is the default. If you specify FPBP64C=N, the buffer manager increases and decreases the number of buffers as needed, but does not release the buffer storage when the number of buffers decreases.

FPBP64D=N | Y

Directs IMS (Y) or tells IMS not (N) to use values on the DBBF parameter to calculate the initial startup sizes for the 64-bit subpools. FPBP64D=N is the default. If you specify FPBP64D=Y, IMS sets the initial total number of buffers for the 64-bit subpools to 25 percent of the value specified on the DBBF parameter and distributes these buffers among all the CI sizes according to an internal algorithm.

For example, if you specify DBBF=4000 and FPBP64D=Y, IMS sets the initial total number of Fast Path buffers to 1000 and distributes them to the subpools.

Each 64-bit subpool must be a minimum of 32 buffers (for a 512-byte buffer - X'200') or 16 buffers for all other sizes.

FPBP64E=N | Y

Specifies whether the Fast Path 64-bit buffer manager increases the number of Fast Path buffers automatically based on an internal buffer-usage monitoring algorithm. FPBP64E=N is the default. If you specify FPBP64E=N, the number of buffers is increased only when a request for a buffer is received and no buffers are available to satisfy that request.

FPBP64MIN=N | Y

Specifies whether the Fast Path 64-bit buffer manager allocates the subpools using the internal algorithm (FPBP64MIN=N) or allocates a subpool with minimum sizes (FPBP64MIN=Y) that vary between 8 and 32 buffers per subpool. FPBP64MIN=N is the default.

FPBP64SR=Y | N

Specifies whether the Fast Path 64-bit buffer manager moves SDEP insert buffers into 64-bit storage during /ERESTART command processing and Extended Recovery Facility (XRF) and FDBR tracking. FPBP64SR=Y is the default. When FPBP64SR=N is specified, IMS uses ECSA for SDEP insert buffers during /ERESTART command processing and Extended Recovery Facility (XRF) and FDBR tracking.

FPBP6HOFF=N | Y

Specified whether the 64-bit /ERE code is enabled for the 64-bit High Speed Sequential Processing (HSSP) and High Speed Reorganization (HSRE) utilities. When FPBP6HOFF=Y is specified, the 64-bit /ERE code is disabled, IMS uses the pre-existing 31-bit private utility buffers to continue the processing during an emergency restart.

FPSISETI=Y | N

Specifies whether to prevent the Fast Path secondary index database maintenance, which you specify by using the SETI psb=psbname statement. FPSISETI=Y is the default.

Y

Specifies that the SETI PSB=psbname parameter on the //DFSCTL DD statement takes effect. Index database maintenance can be performed for the DEDB database.

N

Specifies that SETI PSB=psbname parameter on the //DFSCTL DD statement does not take effect. Index database maintenance cannot be performed for the DEDB database.

See Set Index Maintenance Off (SETI) control statement for more information on the SETI control statement.

MAINSIZE=

Overrides the DFSORT default option for storage to be allocated.

The value is specified as a decimal value, in bytes, kilobytes, or megabytes, where:

xxxxxxxxxx

Bytes. Maximum value is 2097152000.

xxxxxxxK

Kilobytes. Maximum value is 2048000K.

xxxxM

Megabytes. Maximum value is 2000M.

There is no default value for MAINSIZE=.

SDEPAUTO=N | F | T

Specifies whether the Automatic SDEP Buffer Management feature is enabled.

N

Specifies that the feature is disabled.

F

Specifies that the SDEPFREQ parameter is used to determine when processing is started.

T

Specifies that the SDEPTIME parameter is used to determine when processing is started.

When this parameter is omitted, Automatic SDEP Buffer Management is disabled, and the default is SDEPAUTO=N. If an invalid option is specified, the default is taken.

If there is an error in a parameter that occurs earlier in the FASTPATH section, it might cause SDEPAUTO to take the default value even if it is specified.

SDEPEXP=

Specifies the maximum age in minutes of pre-allocated SDEP CIs. The default age is 120 minutes. The minimum age is 60 minutes, and the maximum age is 65,535 minutes. If an invalid age is specified, the default is taken.

If there is an error in a parameter that occurs earlier in the FASTPATH section, it might cause SDEPEXP to take the default value even if it is specified.

SDEPFREQ=

Specifies the number of minutes between checks for expired SDEP CIs. This is only valid for SDEPAUTO=F and is ignored for SDEPAUTO=T. The default is 1440 minutes. The minimum frequency is 60 minutes, and the maximum frequency is 65,535 minutes. If an invalid frequency is specified, the default is taken.

If there is an error in a parameter that occurs earlier in the FASTPATH section, it might cause SDEPFREQ to take the default value even if it is specified.

SDEPTIME=

Specifies the local time of day in 24-hour format to check for expired SDEP CIs. The default is 2300. This is only valid for SDEPAUTO=T and is ignored for SDEPAUTO=F. The valid range for hours is 00 - 23, and the valid range for minutes is 00 - 59. If an invalid time is specified, the default is taken.

If there is an error in a parameter that occurs earlier in the FASTPATH section, it might cause SDEPTIME to take the default value even if it is specified.

VSO1THLD=

Specifies the castout threshold time in seconds for a VSO area with less than or equal to 800 control intervals (CIs). The valid range is 1 - 300. The default value is 300.

VSO2THLD=

Specifies the castout threshold time in seconds for a VSO area with 801 - 3500 CIs. The valid range is 1 - 300. The default value is 240.

VSO3THLD=

Specifies the castout threshold time in seconds for a VSO area with greater than 3500 CIs. The valid range is 1 - 300. The default value is 180.