Managing Transaction Log Buffers and Files

There are configuration options for transaction log buffers and files.

  • Transaction log buffers: There is one transaction log buffer for each database and the size of the transaction log buffer can be configured using the LogBufMB DSN connection attribute.

    Strands divide the transaction log buffer available memory into a number of different regions, which can be accessed concurrently by different connections. The number of transaction log buffer strands is configured with the LogBufParallelism connection attribute. After which, each connection can run data independent DML statements in parallel using those strands as if each has its own transaction log buffer. See LogBufParallelism in the Oracle TimesTen In-Memory Database Reference.

  • Transaction log files: The transaction log files are created in the location that the LogDir connection attribute specifies.

    Note:

    The LogDir connection attribute is optional and if it is not specified, the transaction log files are created in the same directory as the checkpoint files. However, for best performance, TimesTen recommends that you use the LogDir connection attribute to place the transaction log files in a different physical device from the checkpoint files. If separated, I/O operations for checkpoints do not block I/O operations to the transaction log and vice versa.

    If the database is already loaded into RAM and the transaction log files and checkpoint files for your database are on the same physical device, TimesTen writes a message to the daemon log file.

    See LogDir in the Oracle TimesTen In-Memory Database Reference and Check Transaction Log File Use of File System Space in the Oracle TimesTen In-Memory Database Monitoring and Troubleshooting Guide.

    You can configure the maximum size for the transaction log files with the LogFileSize DSN connection attribute. See LogFileSize in the Oracle TimesTen In-Memory Database Reference.

    The transaction log file names have the form dsname.logn. The dsname is the database path name that is specified by the DataStore DSN connection attribute and is provided within the database's DSN. The suffix n is the transaction log file number, starting at zero.

    When the database is created, TimesTen creates reserve files named dsname.res0, dsname.res1, and dsname.res2. These files contain pre-allocated space that serves as reserved transaction log space. Reserved transaction log space allows for a limited continuation of transaction logging if the file system that holds the transaction log files becomes full. If the file system that contains the transaction logs becomes full, the database does not allow any new transactions to begin. Transactions that are in progress are allowed to continue by using the reserve files until they either commit or rollback. If there are transactions that are still in progress and the reserve files are all consumed, all database operations that generate log files are blocked.