internal/Test-DbaLsnChain.ps1
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function Test-DbaLsnChain { <# .SYNOPSIS Checks that a filtered array from Get-FilteredRestore contains a restorabel chain of LSNs .DESCRIPTION Finds the anchoring Full backup (or multiple if it's a striped set). Then filters to ensure that all the backups are from that anchor point (LastLSN) and that they're all on the same RecoveryForkID Then checks that we have either enough Diffs and T-log backups to get to where we want to go. And checks that there is no break between LastLSN and FirstLSN in sequential files .PARAMETER FilterdRestoreFiles This is just an object consisting of the output from Read-DbaBackupHeader. Normally this will have been filtered down to a restorable chain before arriving here. (ie; only 1 anchoring Full backup) .NOTES Original Author: Stuart Moore (@napalmgram), stuart-moore.com dbatools PowerShell module (https://dbatools.io, clemaire@gmail.com) Copyright (C) 2016 Chrissy LeMaire This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. .EXAMPLE Test-DbaLsnChain -FilteredRestoreFiles $FilteredFiles Checks that the Restore chain in $FilteredFiles is complete and can be fully restored #> [CmdletBinding()] Param ( [parameter(Mandatory = $true)] [object[]]$FilteredRestoreFiles ) #Need to anchor with full backup: $FunctionName =(Get-PSCallstack)[0].Command Write-Verbose "$FunctionName - Testing LSN Chain" $FullDBAnchor = $FilteredRestoreFiles | Where-Object {$_.BackupTypeDescription -eq 'Database'} if (($FullDBAnchor | Group-Object -Property FirstLSN | Measure-Object).count -ne 1) { $cnt = ($FullDBAnchor | Group-Object -Property FirstLSN | Measure-Object).count Foreach ($tFile in $FullDBAnchor){write-verbose "$($tfile.FirstLsn) - $($tfile.BackupTypeDescription)"} Write-Verbose "$FunctionName - db count = $cnt" Write-Warning "$FunctionName - More than 1 full backup from a different LSN, or less than 1, neither supported" return $false break; } #Check all the backups relate to the full backup #Via RecoveryForkID: #Allow for striped fill backups: $RecoveryForkID = ($FullDBAnchor | Select-Object -First 1).RecoveryForkID if (($FilteredRestoreFiles | Where-Object {$_.RecoveryForkID -ne $RecoveryForkID}).count -gt 0) { Write-Warning "$FunctionName - Multiple RecoveryForkIDs found, not supported" return $false break } #Via LSN chain: $CheckPointLSN = ($FullDBAnchor | Select-Object -First 1).CheckPointLSN $FullDBLastLSN = ($FullDBAnchor | Select-Object -First 1).LastLSN $BackupWrongLSN = $FilteredRestoreFiles | Where-Object {$_.DatabaseBackupLSN -ne $CheckPointLSN} #Should be 0 in there, if not, lets check that they're from during the full backup if ($BackupWrongLSN.count -gt 0 ) { if (($BackupWrongLSN | Where-Object {$_.LastLSN -lt $FullDBLastLSN}).count -gt 0) { Write-Warning "$FunctionName - We have non matching LSNs - not supported" return $false break; } } $DiffAnchor = $FilteredRestoreFiles | Where-Object {$_.BackupTypeDescription -eq 'Database Differential'} #Check for no more than a single Differential backup if (($DiffAnchor.FirstLSN | Select-Object -unique | Measure-Object).count -gt 1) { Write-Warning "$FunctionName - More than 1 differential backup, not supported" return $false break; } elseif (($DiffAnchor | Measure-Object).count -eq 1) { $TlogAnchor = $DiffAnchor } else { $TlogAnchor = $FullDBAnchor } #Check T-log LSNs form a chain. $TranLogBackups = $FilteredRestoreFiles | Where-Object {$_.BackupTypeDescription -eq 'Transaction Log' -and $_.DatabaseBackupLSN -eq $FullDBAnchor.CheckPointLSN} | Sort-Object -Property LastLSN for ($i=0; $i -lt ($TranLogBackups.count)-1) { if ($i -eq 0) { if ($TranLogBackups[$i].FirstLSN -gt $TlogAnchor.LastLSN) { Write-Warning "$FunctionName - Break in LSN Chain between $($TlogAnchor.BackupPath) and $($TranLogBackups[($i)].BackupPath) " return $false break } }else { if ($TranLogBackups[($i-1)].LastLsn -ne $TranLogBackups[($i)].FirstLSN -and ($TranLogBackups[($i)] -ne $TranLogBackups[($i-1)])) { Write-Warning "$FunctionName - Break in transaction log between $($TranLogBackups[($i-1)].BackupPath) and $($TranLogBackups[($i)].BackupPath) " return $false break } } $i++ } Write-Verbose "$FunctionName - Passed LSN Chain checks" return $true } |