Hi, Here is the function can calculate the no.of files difference between the two wail files, and will give you an exact results. CREATE OR REPLACE FUNCTION public.hot_standby_lag(primary_xlog_loc text, slave_xlog_replay_loc text) RETURNS integer LANGUAGE plpgsql AS $function$ declare Digit_Length int; Query text; No_of_Bits int; No_of_Walfiles int; No_of_Zeros int:=0; Cnt int:=0; Re_Formatted_Primary_Log text; Re_Formatted_Slave_Log text; _1 int; _2 int; _3 int; BEGIN select GREATEST(length(trim(substring($1 for 8),'0')||trim(substring($1 from 9 for 8),'0')||ltrim(substring($1 from 17 for 8),'0')),length(ltrim(substring($2 for 8),'0')||trim(substring($2 from 9 for 8),'0')||ltrim(substring($2 from 17 for 8),'0'))) into Digit_Length; select GREATEST(length(ltrim(substring($1 for 8),'0')),length(ltrim(substring($2 for 8),'0'))) into _1; select GREATEST(length(trim(substring($1 from 9 for 8),'0')),length(trim(...