identified. The analysis methods are different depending on whether the problem is already known or not. If the problem is already well-known there are probably ready made queries that can be used to identify the problem. If the problem is not known, queries are not available and the raw performance counters need to be analysed to classify the problem type. Queries Queries are used to speed up detection of already known performance problems. Already identified problem types do not require further investigation. They are to be detected and corrected as fast as possible (an example is shown in Figure 2.99). Due to the nature of this kind of 'find and fix' work, it is well suited to front line operation and maintenance team. They can run these queries regularly to find out the problems and then to correct them based on available solutions. Analysing Performance Counters There are large numbers of performance indicators. As the systems develop and new features emerge there are likely to be even more. The basic approach is to first look at counters that are used to calculate higher level KPIs. The drop call KPI consists of RAB active failures (see Figure 2.100) that are due to different reasons. The first step is to see what is the distribution of these reasons and whether there are different rea- sons incremented for the failures (RADIO, a radio interface failure; IU, an IU interface failure; RNC, an RNC internal failure). The cells that have the same reason incremented should be checked for similar prob- lems. The same approach can then be used to analyse the RRC setup, RRC active and RAB setup phases. Another example involves two counters that identify cells that have RAB active completions and no RRC connection attempts. This indicates that call setup is not possible in those cells but handovers are working. More complex examples involve correlation analysis of many different variables. High numbers of RAB active completions (low pool capacity and RAB/RRC setup failures due to TRANS (transmission interface failure