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SerializedSystemIni.dat – key to WebLogic’s security

The SerializedSystemIni.dat file is a critical part of every WebLogic domain and if not administered properly, could result in your servers not starting and you having to recreate the entire domain. So, a good understanding of this file is important.


What is it?

SerializedSystemIni.dat is a WebLogic domain file which contains hashes.  Currently, these hashes use Triple-DES block ciphers (that’s why the encrypted passwords begin with “{3DES}”). SerializedSystemIni.dat is located in the domain directory (WebLogic Server 8.1 and earlier) or in domain/security directory (WebLogic Server 9.x and later).


When and how is it created?

The SerializedSystemIni.dat is created during the creation of a WebLogic domain. The hashes in the file are created using an algorithm that binds the file to the domain in which it has been created. So, a SerializedSystemIni.dat file can be used only within the domain in which it has been created (cannot be used in other WebLogic domains). Also, in WebLogic Server versions 8.1 SP6 and earlier, the SerializedSystemIni.dat file (along with msi-config.xml and files)  is replicated into a managed server’s root directory every 5 minutes for managed servers which have MSI File Replication enabled. These files are replicated even if the admin and managed servers share the same server root directory (doesn’t make sense to me).


What is it used for?

SerializedSystemIni.dat is used for encryption/decryption of plain-text/ciphertext within a WebLogic domain.


  • If SerializedSystemIni.dat is corrupted (modified) or missing, then the WebLogic Servers in your domain will not start and you will have to reconfigure the domain.
  • If MSI File Replication is enabled for your managed servers in domains running on WebLogic server versions 8.1 SP6 or earlier, then a bug in the 5-minute replication could cause corruption of SerializedSystemIni.dat occasionally during server restart and will make it a zero-byte file if the disk drive or mountpoint in which the WebLogic domain is located is 100% full.
  • If SerializedSystemIni.dat is transferred to its domain in ascii mode (for example, from a configuration management system) , the file could become corrupted.


Best Practices

  • Ensure that you have a working backup of SerializedSystemIni.dat. i.e. test the recovery of SerializedSystemIni.dat and server start-up using the backup copy.
  • If you’re using WebLogic Server versions 8.1 SP6 or earlier and have MSI File Replication enabled, then ensure you contact Oracle, obtain and deploy patch CR260218 (Guardian Signature Patterns Release 1.1.34 and Signature ID 000168) to fix the bug in replication that corrupts SerializedSystemIni.dat or makes it a zero-byte file.
  • If you require to transfer SerializedSystemIni.dat to its domain via FTP, always use binary mode for the file transfer.
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