FASTPATH section of the DFSDFxxx member

The FASTPATH section of the DFSDFxxx member specifies options for Fast Path, such as the use of the Fast Path 64-bit buffer manager. The section must begin with the header <SECTION=FASTPATH>. Start of change The FASTPATH section is valid in DB/DC and DBCTL environments. End of change

Syntax


>>-+---------------+--+----------------+------------------------>
   '-ACBSHR=-+-Y-+-'  '-ALTERGRP=xxxxx-'   
             '-N-'                         

   .-ALTERHLQ=DBFUDAWK-.  .-FPBP64=N--------------------.   
>--+-------------------+--+-----------------------------+------->
   '-ALTERHLQ=hlqname--'  '-FPBP64=Y-+-FPBP64M=xxxxx--+-'   
                                     +-FPBP64M=xxxxxK-+     
                                     '-FPBP64M=xxxxM--'     

   .-FPBP64C=N-.  .-FPBP64D=N-.  .-FPBP64E=Y-.   
>--+-----------+--+-----------+--+-----------+------------------>
   '-FPBP64C=Y-'  '-FPBP64D=Y-'  '-FPBP64E=N-'   

   .-FPBP64SR=Y-.  .-FPBP64MIN=N-.   
>--+------------+--+-------------+------------------------------>
   '-FPBP64SR=N-'  '-FPBP64MIN=Y-'   

>--+--------------------------+--+------------+----------------->
   '-MAINSIZE=-+-xxxxxxxxxx-+-'  '-VSO1THLD=n-'   
               +-xxxxxxxK---+                     
               '-xxxxM------'                     

>--+------------+--+------------+------------------------------><
   '-VSO2THLD=n-'  '-VSO3THLD=n-'

Parameters

ACBSHR=

Specifies whether the ACB libraries are shared among the IMS™ systems. 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:

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

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: Start of change

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. End of change

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. End of change

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. End of change

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.

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=.

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. End of change

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. End of change

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. End of change

Example of the FASTPATH section of the DFSDFxxx member

/******************************************************************/
/* Fast Path Section                                              */
/******************************************************************/
<SECTION=FASTPATH>
FPBP64=Y                       /* Fast Path 64-bit buffer manager */
FPBP64M=2047M                  /* FP 64-bit buffer pool max limit */
/******************************************************************/
/*                                                                */
/******************************************************************/