How to avoid performance issues after converting oracle RAC to Single instance?

Hi everyone,

 Does someone know how to calculate the correct settings for oracle parameters (i.e. memory, etc) after migrating to Single Instance?

 In my case I have 4 instances each one with this values

SELECT name, (value/1024)/1024 Mb
FROM v$parameter WHERE name IN
('shared_pool_size', 'java_pool_size', 'streams_pool_size',
'log_buffer', 'db_cache_size', 'db_keep_cache_size', 'db_recycle_cache_size',
'large_pool_size','sga_max_size')
ORDER BY 2 desc
NAME MB
---------------------------------------------------------------- ----------
sga_max_size 4058.97646
db_keep_cache_size 1200
db_cache_size 1024
shared_pool_size 704
db_recycle_cache_size 512
java_pool_size 128
large_pool_size 64