High TAS collision rate 
High TAS collision rate
High TAS collision rate: <number> per region accesses, <number of> TAS collisions, <number of> region accesses
Explanation
There is a very high collision rate when accessing internal database semaphores during region access. See also
High collision rate on <name> region. If the parameters are set correctly, this problem is only observed on multi-CPU machines or with a high UKP number (XPARAM parameter MAXCPU > 4).User action
The likelihood of TAS collision increases as the number of the UKPs increases (XPARAM parameter MAXCPU). You should therefore check multiprocessor systems to determine whether the database might still be able to adequately handle the application requirements with fewer CPUs. In the R/3 environment the ratio of CPU usage between the database and R/3 is approximately 1:4; this means that on an eight-CPU machine, two CPUs will be sufficient for SAP DB. These calculations can also be made for client/server architectures.
If the database is running on a pure database server (client/server), the number of UKPs should be at least one less than the number of CPUs on systems with four or more CPUs. If TAS collisions still occur, set the XPARAM parameter _MP_RGN_DIRTY_READ to YES.
If a large number of TAS collisions occur in centralized multiprocessor systems with less than four UKPs (XPARAM parameter MAXCPU), check whether the machine is CPU-bound with the database processes blocked by the application. If this is the case, those database processes that contain user tasks should receive REAL TIME PRIORITY from the operating system. Make sure, however, that MAXCPU is at least one less than the actual number of CPUs.