1. 初始化 ThisTimeLineID、RedoRecPtr
函數 InitXLOGAccess() 內部會初始化 ThisTimeLineID、wal_segment_size、doPageWrites 和 RedoRecPtr 等全局變量。
下面是這四個變量初始化前的值：
- (gdb) p ThisTimeLineID
$125 =0
(gdb) p wal_segment_size
$126 =16777216
(gdb) p doPageWrites
$127 =false
(gdb) p RedoRecPtr
$128 =0
XlogCtl 變量成員初始化情況如下：
- (gdb) p
*XLogCtl
$130 = {
Insert = {
insertpos_lck = 0 ‘\000’,
CurrBytePos = 22421680,
PrevBytePos = 22421624,
pad = ‘\000’ <repeat
