W2K8 R2 WINS adds support for dynamic jet cache size with optional registry keys to tune jet database cache size


Symptoms


Name queries to pre-Windows Server 2008 R2 WINS Servers may take a longer amount of time to resolve as additional records are added to the WINS jet database and the WINS Server is tasked with resolving a large number of name queries.

The inability by a WINS Server to quickly resolve name queries may result in resource exhaustion or reduced transactional throughput on application servers or domain controllers issuing or relying on such name queries.

Cause


The size of the jet database cache on pre-Windows Server 2008 R2 WINS Servers is hard-coded to a relatively small value which may be insufficient to cache a sufficient number of records as a WINS database grows in size or experiences increased query volume.

When the WINS Sever jet cache is not allowed to grow so that records in increasely large WINS databases can be cached, WINS Server throughput becomes disk-bound and name query performance degrades sharply.

Environments with large WINS databases, small, fixed jet cache sizes and high query volumes represent a worst-case scenario for WINS performance.

Resolution


Replace or upgrade WINS Servers running pre-Windows Server 2008 R2 with WINS Servers running Windows Server 2008 R2 to obtain the following benefits:

  1. The WINS Server will dynamically adjust the size of the jet database cache based on the size of and query patterns against the WINS database.

    Note: This assumes there is no memory presure constraining memory utilization on the WINS Service.
  2. Support for 2 new registry entries which allow administrators to define minimum and maximum jet cache sizes read by the WINS Service at service start.

More Information


To override automatic control of the jet database cache sizes in Windows Server 2008 R2, the JetDbMaxCacheSize and JetDbMinCacheSize must be created at the following registry path:

Registry subkey: HKLM\System\CurrentControlSet\Services\WINS\Parameters

Registry entry: JetDbMaxCacheSize
Data type: REG_DWORD
Default value: 0
Description: This value defines the maximum size of the WINS database size, in KB. This value must be greater than the value set for JetDbMinCacheSize. If a value for JetDbMaxCacheSize is set that is less than JetDbMinCacheSize, then WINS will auto tuning for the maximum cache size.

Registry entry: JetDbMinCacheSize
Data type: REG_DWORD
Default value: 0
Description: This value defines the minimum size of the WINS database size, in KB. The minimum allowed value is 2. If a value of less than 2 is set, WINS will set the minimum cache size at 2KB.

When the entries are not present or set to 0, WINS Server will automatically adjust the size of its cache as a function of database and machine activity levels.

Microsoft recommends that you let the W2K8 R2 WINS Server service dynamically define the jet database cache size.