How To Analyze wait: ‘enq: HW – contention’

This wait can have an impact to production and deteriorate performance on a DB, so lets investigateā€¦ Lets see the output from a AWR report where this event is 23% of the total wait time: As per “Analyzing ‘enq: HW – contention’ Wait Event (Doc ID 740075.1)”, this can be generated by multiple sessions fighting... » read more

df vs. du: why so much difference?

Sometimes you might get an incident for high usage on a filesystem. You check and yes, filesystem usage is high, but ‘du’ (disk usage) if different. why? Some explanations might say: they don’t use the same methods or metrics to calculate what they are reporting.Yes, that’s true, but pretty much outputs should be the same.If... » read more

ORA-16191: Primary log shipping client not logged on standby

This error usually is because of password file mismatch: someone updated in primary and forgot to pass across to standby nodes, missed a nodeā€¦ but what if password file in primary and standby is the same? In this case, password files are correct so PRIMARY should not have issues sending logs,right? But no, instead it... » read more

RMAN: HOW TO REFRESH a DB from backup

Lets suppose you have been requested to refresh a TEST/DEV Database and you don’t have access to the source DB, just access to the backups someone created. In this case, this is a Windows environment and we are going to assume the following information: DB and Archive log backups located under: “D:\RMAN\Backup\”Control file backup to... » read more

ORA-27106: system pages not available to allocate memory

If you have set use_large_pages=ONLY, server need to have enough huge pages to allocate the SGA in the number of pages available, if not, you might get this error while trying to start instance: In this system you have only enough pages to allocate 17G and you require 28G, not good.How do you fix? You... » read more