Reads Exhausted are the number of times within the sampling interval where there were no read buffers available to the OSA or HiperSockets device upon entry to the queued direct I/O (QDIO) program-controlled interrupt (PCI) Exit.
If this value is not zero, this might indicate a lack of read buffers for the queued direct I/O (QDIO) datapath device. It is likely a lack of read buffers will result in dropped packets and therefore packet retransmission.
This situation is caused by the OSA or HiperSockets device overrunning the queued direct I/O (QDIO) program-controlled interrupt (PCI) Exit. To help prevent a Reads Exhausted condition, provide the device with a larger set of SBALs (Storage Block Address Lists). An SBAL is a set of 16 4K read buffers and therefore a 64K read buiffer. A maximum of 126 SBALs are allowed. Issue the Display TRLE VTAM command and note the value displayed for message IST2333I. Note the number of SBALs under the READ STORAGE header. If possible, increase this value to help prevent a Reads Exhausted condition. For information about how many SBALs VTAM allocates by default for each OSA-Express QDIO and HiperSockets interface, how to control the amount of this storage allocation using the VTAM QDIOSTG start option (for OSA-Express QDIO) and the VTAM IQDIOSTG start option (for HiperSockets), see the IBM z/OS Communications Server: SNA Resource Definition Reference.
The READSTORAGE parameter for the DEVICE/LINK and INTERFACE statement overrides the QDIOSTG and IQDIOSTG parms. For more information, see the IBM z/OS Communications Server IP Configuration Reference.
If the number of SBALs is already at the maximum, contact IBM Software Support to determine if there are other reasons for the reads exhausted situation to occur.
This is a critical situation.
Formula: Reads Exhausted > 0