errno 63 (ENOSR): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: out of streams resources

Could be also:
Constant	Type	OS
ERROR_PRINT_CANCELLED	Win32 error	Windows
STATUS_WAIT_63	NTSTATUS	Windows
ENOSR	errno	Linux
ENAMETOOLONG	errno	Mac
NO_MORE_SYSTEM_PTES	BugCheck Code	Windows

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ENOSR

ENOSR is Solaris errno value 63, Out of stream resources. Oracle documents a precise STREAMS open-time failure: no STREAMS queues or no stream-head data structures were available. The condition is described as temporary because another process can release the required resources.

Look for STREAMS resource pressure, not malformed data

Record which device or STREAMS endpoint was being opened and how frequently the application creates and closes streams. A burst of opens can exhaust a finite pool temporarily, while a persistent increase can indicate descriptors or stream instances that are not being released. The module stack matters because opening a stream can allocate queues for modules as well as the stream head.

A retry with sensible backoff may succeed after resources are freed. A tight loop that continuously opens more streams can make the shortage worse. ENOSR is distinct from ENOSTR, which means a STREAMS-specific operation was applied to a descriptor that is not a stream, and from EBADMSG, which concerns an incompatible message at the stream head.

References

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