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IBM's Local Shared Resources (LSR) facility allows the sharing of common control blocks such as I/O control blocks, buffers, and channel programs. Using this facility increases performance when queuing and processing transfer requests. To use the IBM LSR facility, the BLSR region has to be started. In the JCL used to start the XCOMXFER STC, make the following JCL change.
Note: LSR is recommended only for installations with very high volumes of scheduled transfers that are being run concurrently. EXECUTE transfers do not use XCOMRRDS, thus installations running a high volume of TYPE=EXECUTE transfers do not benefit from using LSR.
To configure for LSR support
Change this line:
//XCOMRRDS DD DSN=XCOM.RRDS,DISP=SHR
to:
//DSVXRRDS DD DISP=SHR,DSN=XCOM.RRDS //XCOMRRDS DD SUBSYS=(BLSR,'DDNAME=DSVXRRDS', // 'BUFND=302', // 'STRNO=151', // 'RMODEB0=ALL', // 'DEFERW=NO')
The recommended settings for the XCOMRRDS parameters are as follows:
2 * (MAXTASK +1)
For example, if MAXTASK=150 then these parameters need to be set to 2 * (150 + 1) which is 302.
MAXTASK + 1
For example, if MAXTASK=150 then this parameter should be set to 151.
ALL indicates that buffers above the 16 MB line are being used.
Indicates whether VSAM deferred write (DFR) is to be used.
Note: Setting this parameter to NO causes data to be written to disk, ensuring that transfer information is not lost if an abnormal termination occurs. However, setting this parameter to NO decreases performance, because data is written to disk instead of to memory.
Setting DEFERW to YES improves performance, but if an abnormal termination occurs with this parameter set to YES, data that is written to memory is lost because it will not have been written out to the XCOMRRDS data set.
For more detailed information about the IBM LSR facility, see the online IBM documentation.
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