r data. When analysing PLMN parameters, check that no inconsistencies remain in the roaming profile data. The most reliable way to ensure this is to format all profile data relative to the PLMN analysed. The counter values mean that, for example, when the location update counter is 5, the operation (IMEI checking, TMSI allocation or authentication) is done with every fifth location update registered in the VLRU. If the counter value is 1, this means that the operation in question is done every time it is registered in the VLR. If the counter value is 0, this means that the counter is not used. HLR Configuration Parameters Audit The HLR-specific parameters are general parameters of the HLR (i.e. they do not depend on the PLMN, for example). These various parameters define the HLR actions in more detail and affect all subscribers in the HLR. In PLMN records the operation of the HLR with other networks is determined. The PLMN record specifies whether: a subscriber is removed from the VLR when the update fails in that PLMN; roaming is not allowed to a PLMN for subscribers with certain services; there are supplementary or basic services that must not be transferred to the PLMN where a subscriber is roaming. The HLR parameters need to be studied well to determine if there are any inconsistencies in parameter selection that could lead to failures in the network. A good example is the maximum number of call forwarding that is set in the HLR. This parameter should be the same in all HLRs in the network. When the operator makes changes in the subscriber data, the changes need to be transferred from the HLR to the VLR. The parameter number of insert attempts and the interval between insert attempts define how many update attempts are made and how long a delay there is between the attempts to update the subscriber data. HLR PLMN Parameters Audit The PLMN-specific parameters control HLR functions that depend on the PLMN (or even on the VLR) where the subscriber is roaming. This shows how the HLR operates with other networks. 