But === **Linear solvers are in fact omnipresent in the flow of** **Code_Aster** operators because they are often buried in the depths of other numerical algorithms: non-linear schema, time integration, modal analysis etc. They often consume most of the CPU time and memory. The choice and complete configuration of the required linear solver is made*via* the keyword factor SOLVEUR. It is present in most calculation commands (STAT_NON_LINE, THER_LINEAIRE, CALC_MODES etc.). This **user manual is complementary to the User documentation** for the keyword SOLVEUR [U4.50.01]. It is intended to be an intermediate link between "simple" keyword documentation and theoretical documentation (each solver is backed by reference documentation). The first part of this note gives an **overview** of the various linear solvers available, their scope of use and their average performances in terms of robustness and CPU /memory consumption. The next chapter contains some **advice** to make the best use of the SOLVEUR parameters depending on the case: the size of the system, its numerical properties, the CPU and memory consumption... Finally, we detail some parameters of SOLVEUR in order to help the user in **advanced usage** of this code feature. The **related problems** of improving the performance (RAM/CPU) of a calculation and the use of parallelism are also briefly addressed. They are the subject of specific notices, respectively, [:ref:`U1.03.03 `] and [:external:ref:`U2.08.06 `].