Expert Advice

N3T_DLC_Read_Deferrals  
Situation Description
Suggested Actions
Read Processing Deferrals is greater than 0

 

Reads Exhausted represents the number of reads exhausted due to full read buffers during the most recent sampling interval.

A read processing deferral occurs when the queued direct I/O (QDIO) program-controlled interrupt (PCI) Exit must defer processing of read completions because a control block cannot be obtained to represent the inbound data. Read processing deferrals for the primary and all ancillary read queues are consolidated into the primary read queue count.

Each OSA-Express QDIO and HiperSockets interface requires fixed storage for read processing (which is allocated by VTAM). This storage is acquired from CSM 4K ECSA. If you define a large number of these interfaces (for example, by configuring multiple VLANs to one or more OSA-Express features), then you need to consider how much fixed Communications Storage Manager (CSM) 4K Extended Common System Area (ECSA) storage your configuration requires. For information about considerations for the IVTPRM00 parmlib member, see IBM z/OS Communications Server: SNA Resource Definition Reference.

If you believe you have sufficient limits on CSM 4K ECSA, the OSA or HiperSockets device may be overrunning the interrupt exit. In this case an internal modification to VTAM may be warranted.

This is a critical situation.

 

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