獲得Redo Block Size的非典型方法

2024-07-21 02:32:59

字體：大中小

供稿：網(wǎng)友

我以前介紹過(guò)獲得redo block size的方法，當(dāng)然也可以通過(guò)dbfsize工具獲得。現(xiàn)在在這里我想介紹的是另外一種非典型方法，有多非典型呢? 問(wèn)題來(lái)自于N年前我在一個(gè)客戶(hù)的機(jī)器上部署的監(jiān)控腳本，現(xiàn)在那些腳本看來(lái)還在運(yùn)行著，我最近收到了大量類(lèi)似如下內(nèi)容的郵件:

ORA-16038: log 2 sequence# 17151 cannot be archived
ORA-19504: failed to create file ""
ORA-00312: online log 2 thread 1: '/eXPort/home/Oracle/oradata/cuwap/redo02.log'
ORA-19504: failed to create file "/data1/oraarc/PTL017151.arc"
ORA-19504: failed to create file "/data1/oraarc/PTL017151.arc"
ORA-27044: unable to write the header block of file
ORA-16038: log 2 sequence# 17151 cannot be archived
ORA-19504: failed to create file ""
ORA-00312: online log 2 thread 1: '/export/home/oracle/oradata/cuwap/redo02.log'
ORA-19504: failed to create file "/data1/oraarc/PTL017151.arc"
ORA-19504: failed to create file "/data1/oraarc/PTL017151.arc"
ORA-27044: unable to write the header block of file
ORA-16038: log 2 sequence# 17151 cannot be archived
ORA-19504: failed to create file ""
ORA-00312: online log 2 thread 1: '/export/home/oracle/oradata/cuwap/redo02.log'
ORA-19502: write error on file "/data1/oraarc/PTL017151.arc", blockno 169985 (blocksize=512)
ORA-27072: skgfdisp: I/O error
ORA-19502: write error on file "/data1/oraarc/PTL017151.arc", blockno 169985 (blocksize=512)
ORA-19502: write error on file "/data1/oraarc/PTL017152.arc", blockno 57345 (blocksize=512)
ORA-27072: skgfdisp: I/O error
ORA-19502: write error on file "/data1/oraarc/PTL017152.arc", blockno 57345 (blocksize=512)
ORA-16038: log 2 sequence# 17151 cannot be archived
ORA-19502: write error on file "", blockno (blocksize=)
ORA-00312: online log 2 thread 1: '/export/home/oracle/oradata/cuwap/redo02.log'
ORA-16038: log 2 sequence# 17151 cannot be archived
ORA-19502: write error on file "", blockno (blocksize=)
ORA-00312: online log 2 thread 1: '/export/home/oracle/oradata/cuwap/redo02.log'
ORA-16038: log 2 sequence# 17151 cannot be archived
ORA-19502: write error on file "", blockno (blocksize=)
ORA-00312: online log 2 thread 1: '/export/home/oracle/oradata/cuwap/redo02.log'
ORA-16038: log 3 sequence# 17152 cannot be archived
ORA-19502: write error on file "", blockno (blocksize=)
ORA-00312: online log 3 thread 1: '/export/home/oracle/oradata/cuwap/redo03.log'

我們注重到，在這些錯(cuò)誤信息中，這樣的提示至關(guān)重要:

ORA-19502: write error on file "/data1/oraarc/PTL017151.arc", blockno 169985 (blocksize=512)
ORA-27072: skgfdisp: I/O error
ORA-19502: write error on file "/data1/oraarc/PTL017151.arc", blockno 169985 (blocksize=512)
ORA-19502: write error on file "/data1/oraarc/PTL017152.arc", blockno 57345 (blocksize=512)

這里的Blocksize就告訴我們，在該系統(tǒng)上（Solaris），Redo Block Size是512 bytes。這里的BlockNo讓我想到了另外一個(gè)內(nèi)容。參考Steve Adams網(wǎng)站上的關(guān)于Log Buffer Usage的說(shuō)明我們能找到另外一個(gè)有意思的內(nèi)容，引用一下Steve的圖：
獲得Redo Block Size的非典型方法

我們知道，Redo Log Buffer和Redo Log File是通過(guò)Block映射（map）來(lái)完成空間分配和使用的，于是也就有了兩個(gè)變量：
1.用以標(biāo)示SGA中Redo Log Buffer基準(zhǔn)位置的變量b
2.用以標(biāo)示Redo Log File基準(zhǔn)位置的變量i 假如這里存在問(wèn)題的是redo log file,那么無(wú)法寫(xiě)入的blockno實(shí)際上就應(yīng)該和variable (i)有關(guān)；當(dāng)然對(duì)于歸檔日志文件，這里的blockno自然也是由最初的變量推進(jìn)和定界的。由以上輸出的錯(cuò)誤信息我們可以知道: