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Facts on SAP Applications running on MS SQL Server with VMware software

Tuesday, 31 July 2012 13:20

Written by Prabakaran Subbarayalu

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SAP Application servers running on VMWare servers receiving frequent 10054 errors or disconnect to from database or Communication Link Failure between application server and database servers.

SAP recommends to follow the OSS Note:

 

1478133 - MS SQL Server: How to analyze connection problems to database server

Even after following all the recommendations mentioned in this Note there errors were continued.

Further analysis it has been identified that the disconnect issues happening during VMWare snapshot and deletion time.

According to VMWare KB Article http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1015180

If the snapshot includes the memory option, the ESX host writes the memory of the virtual machine to disk.
Note: The virtual machine is stunned throughout the duration of time the memory is being written. The length of time of the stun cannot be pre-calculated, and is dependent on the performance of the disk in question and the amount of memory being written. .

The same has been confirmed from VMWare support also by raising a call and with below their comments.

a)    “stun/freeze” is an unavoidable issue which is working as designed.

b)    This behaviour is by design and there is no easy workaround.

c)    The amount of time the VM is stopped is directly dependant on the ESX host load, on the storage load and so on.

d)    For the problematic VMs, it would be good idea to migrate it to a dedicated datastore, so I/O operations will be efficient.

As a work around we have changed the VMWare servers snapshot frequency from daily to weekly, since then the amount of errors have drastically reduced rather completed removed.

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Facts on SAP Applications running on MS SQL Server with VMware software