Below is the simple method to remove the parameter from spfile
-- Check parameter
orasmk@ebssitap:~$ strings $ORACLE_HOME/dbs/spfileEBSSMK.ora | grep optimizer_dynamic_sampling
*.optimizer_dynamic_sampling=2
orasmk@ebssitap:~$
-- remove parameter
alter system reset "optimizer_dynamic_sampling" scope=spfile sid='*';
alter system reset "__db_cache_size" scope=spfile sid='EBSSMK';
-- check in spfile
orasmk@ebssitap:~$ strings $ORACLE_HOME/dbs/spfileEBSSMK.ora | grep optimizer_dynamic_sampling
orasmk@ebssitap:~$
Below is the grep command to check the parameters in spfile
strings $ORACLE_HOME/dbs/spfileEBSSMK.ora | egrep '_always_anti_join|_always_semi_join|_complex_view_merging|_index_join_enabled|_kks_use_mutex_pin|_new_initial_join_orders|_optimizer_cost_based_transformation|_optimizer_cost_model|_optimizer_mode_force|_optimizer_undo_changes|_or_expand_nvl_predicate|_ordered_nested_loop|_push_join_predicate|_push_join_union_view|_shared_pool_reserved_min_alloc|_sortmerge_inequality_join_off|_sqlexec_progression_cost|_table_scan_cost_plus_one|_unnest_subquery|_use_column_stats_for_function|always_anti_join|always_semi_join|background_dump_dest|core_dump_dest|db_block_buffers|db_cache_size|db_file_multiblock_read_count|DRS_START|enqueue_resources|event|hash_area_size|java_pool_size|job_queue_interval|large_pool_size|max_enabled_roles|nls_language|optimizer_dynamic_sampling|optimizer_features_enable|optimizer_index_caching|optimizer_index_cost_adj|optimizer_max_permutations|optimizer_mode|optimizer_percent_parallel|parallel_instance_group|instance_groups|plsql_compiler_flags|plsql_native_library_dir|plsql_native_library_subdir_count|plsql_optimize_level|query_rewrite_enabled|rollback_segments|row_locking|sort_area_size|sql_trace|SQL_VERSION|timed_statistics|undo_retention|undo_suppress_errors|user_dump_dest'
