Data Warehouse Jobs Slow with 'Direct path read' and 'Db file sequential read' Waits
(Doc ID 2387628.1)
Last updated on NOVEMBER 06, 2019
Applies to:Oracle Database - Enterprise Edition - Version 10.2.0.4 and later
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Information in this document applies to any platform.
- Data warehouse jobs slow with following waits:
Top 5 Timed Events
Event Waits Time(s) Avg Wait(ms) % Total Call Time Wait Class
direct path read 10,066,164 618,417 61 32.9 User I/O >>>>>>>>>>>>>>>>>>>>>>top wait events are IO wait events
db file sequential read 12,346,527 399,155 32 21.2 User I/O
PX Deq Credit: send blkd 20,325,278 157,409 8 8.4 Other
db file scattered read 1,907,206 155,578 82 8.3 User I/O
"Avg wait (ms)" column from above section are beyond 10 (ms)> Ideally this should be under 10 (ms), values beyond 10(ms) shows that something may be wrong with IO subsystem.
These values indicate that IO is running slow.
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