(1) .-IQDIOSTG--=--MAX-------. >>-+------------------------+---------------------------------->< '-IQDIOSTG--=--+-MAX-+---' +-AVG-+ +-MIN-+ '-nnn-'
- This option only affects iQDIO devices that use a MFS of 64k. The smaller frame sizes will always use 126 SBALs.
Specifies how much storage VTAM® keeps available for read processing for all HiperSockets™ data devices that use a MFS (Maximum Frame Size) of 64k. The HiperSockets MFS is defined in HCD. The HiperSockets storage units are defined in QDIO SBALs (QDIO read buffers). Each SBAL is 64k. For most users, the default setting will be the most suitable option. The storage used for this read processing is allocated from CSM data space 4k pool, and is fixed storage.
HiperSockets devices that are defined with a smaller MFS (16k, 24k, or 40k) are not affected by this start option. Those devices will use 126 SBALs.
The recommended values can be configured by specifying MAX, AVG, or MIN, which are predefined constants (number of SBALs) that are most appropriate for this type of adapter. MAX allows for the best performance (for example, throughput), but requires more storage. Conversely, MIN could be used for devices with lighter workloads or where system storage might be constrained. Also, instead of using one of the 3 predefined values, users can instead define a specific value for IQDIOSTG (the exact number of SBALs), such as IQDIOSTG=100. The supported range is 8 (minimum supported value) to 126 (maximum supported value). The predefined and possible user defined values for IQDIOSTG are:
- IQDIOSTG=MAX
- Specifies the recommended maximum (126 SBALs for a total of 7.8 MB). This is the default setting.
- IQDIOSTG=AVG
- Specifies the recommended average (96 SBALs for a total of 6 MB).
- IQDIOSTG=MIN
- Specifies the recommended minimum (64 SBALs for a total of 4 MB).
- IQDIOSTG=nnn
- Specifies the user defined specific number of SBALs, valid range of 8 - 126 (see Note 1).
- If you elect to define a specific value versus the recommended values, carefully evaluate your system storage and performance needs for your HiperSockets devices. The amount of storage used is (NNN x 64k) x number of active iQDIO data devices.
- You can use VTAM tuning stats to evaluate your needs and usage. Under a sample (typical) workload, the NOREADS counter should remain low (close to 0). If this count does not remain low you might need to consider a higher setting for IQDIOSTG. RMF™ can also be used to evaluate the correct setting for your environment. RMF records send failures, which can be an indication that the target LP (logical partition) does not have enough storage (read SBALs).
- You can override the IQDIOSTG value for a given HiperSockets device by using the READSTORAGE parameter on the IPAQIDIO LINK, the IPAQIDIO INTERFACE, or the IPAQIDIO6 INTERFACE statement in the TCP/IP profile.