What is that checkbox that says v2 compatibility mean? the help files tell me nothing.
Sachin's right. In version 2.x x of sqlserver probe, some of the QoS definitions did not include samplemax. When version 3.xx was released some of the probe's QoS definitions were enhanced to include a samplemax where there had not been one before. While this is great for new deployments, it's problematic on existing deployments.
If one has been running Version 2.xx of the probe, one's QoS definitions do not include samplemax; the data_engine accepts QoS_MESSAGES without a samplemax field in the PDS and inserts the rows into the relevant QoS table. If one then upgrades to version 3.x, suddenly the sqlserver probe is publishing the same QOS_MESSAGEs but now the PDS contains a samplemax field.
Because the QOS_MESSAGE (with samplemax) does not match the QOS_DEFINITION (without samplemax) nor the QoS table itself, the data_engine is unable to insert the sample into the database and instead drops the qos sample on the floor. (There's a message in the data_engine log as well indicating the QOS_MESSAGE was dropped.)
To prevent this, the V2 Compatibility mode instructs the probe to use the old (no samplemax) definitions and message formats. In short, if one has ANY sqlserver probe generated objects in the NIS database that were inserted by a version 2 probe, then one will want to set the version 3 probe to be version 2 compatible. On the other hand, if the sqlserver probe has never been introduced into the NMS system, then it's perfectly good to run the probe in the native (version 3) mode.
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