execution time of PowerShell script vastly differs between first and second run - sql

Question

I'm facing something really strange when executing a little PowerShell script that fetches some information of a local Oralce DB and put the results into objects. The first execution of this scipt takes about 30 seconds, consecutive executions just as much as 2 seconds!
Does anybody have an explanation for this? (is it caching in the Oracle-DB? / any way to figure out what is causing the speed burst on the second run?)
function Get-SQLConnection
{
Add-Type -Path $(Join-Path $PSScriptRoot "libs/Oracle.ManagedDataAccess.dll")
$connectionString = 'User Id=FOO;Password=BAR;Data Source=TNSCONNID'
return New-Object Oracle.ManagedDataAccess.Client.OracleConnection($connectionString)
}
function Get-SQLIssueQuery($version)
{
$version = $version.ToString()
return "SELECT ...
FROM ... WHERE $version ..."
}
function Get-IssuesForVersion($dbconn, $version)
{
Write-Verbose "Get-IssuesForVersion $($version.ToString())..."
$issues = #{}
$command=$dbconn.CreateCommand()
$command.CommandText=$(Get-SQLIssueQuery $version)
$reader=$command.ExecuteReader()
while ($reader.Read()) {
$text = $reader[0]
[int]$key = $reader[2].Split("-")[1]
$type = $reader[6]
...
$issues[$key] = [Issue]::new($key, $type, ...)
}
Write-KSDetail "Get-IssuesForVersion '$($version.ToString())' returned $($issues.Count) issues..."
return $issues
}
$timestart = $(Get-Date)
$conn = Get-SQLConnection
$conn.open()
Get-IssuesForVersion $conn "Version XYZ"
$conn.close()
$timeend = $(Get-Date)
$duration = $timeend - $timestart # first run: approx 30 seconds
$timestart = $(Get-Date)
$conn = Get-SQLConnection
$conn.open()
Get-IssuesForVersion $conn "Version XYZ"
$conn.close()
$timeend = $(Get-Date)
$duration = $timeend - $timestart # second run: approx 2 seconds
thanks in advance!