pg_resetxlog、pg_resetwal工具的两个用法

-x：
A safe value for the next transaction ID (-x) can be determined by looking for the numerically
largest file name in the directory pg_clog under the data directory, adding one, and then multiplying by 1048576. Note that the file names are in hexadecimal. It is usually easiest to specify the option value in hexadecimal too. For example, if 0011 is the largest entry in pg_clog, -x 0x1200000 will work (five trailing zeroes provide the proper multiplier).

-m：
A safe value for the next multitransaction ID (-m) can be determined by looking for the numerically largest file name in the directory pg_multixact/offsets under the data directory, adding one,and then multiplying by 65536. As above, the file names are in hexadecimal, so the easiest way to do this is to specify the option value in hexadecimal and add four zeroes

-O：
A safe value for the next multitransaction offset (-O) can be determined by looking for the numerically largest file name in the directory pg_multixact/members under the data directory, adding one, and then multiplying by 65536. As above, the file names are in hexadecimal, so the easiest way to do this is to specify the option value in hexadecimal and add four zeroes

-l：
The WAL starting address (-l) should be larger than any WAL segment file name currently existing
in the directory pg_xlog under the data directory. These names are also in hexadecimal and have
three parts. The first part is the “timeline ID” and should usually be kept the same. Do not choose a value larger than 255 (0xFF) for the third part; instead increment the second part and reset the third part to 0. For example, if 00000001000000320000004A is the largest entry in pg_xlog, -l 0x1,0x32,0x4B will work; but if the largest entry is 000000010000003A000000FF, choose -l 0x1,0x3B,0x0 or more.