Stata and ODBC: Connection Persistence During Long-Running Queries

Stata does not implement any native keep-alive mechanisms for ODBC connections. When you execute an odbc load command, Stata enters a blocking state, waiting for the ODBC driver to return the full recordset. The persistence of the connection during this wait is managed entirely by the ODBC driver manager, the specific driver configuration, and the operating system's TCP stack.

Because Stata relies on the system's configured DSN, the application cannot independently signal the driver to keep a specific cursor active or prevent a timeout. If the database server or a network gateway times out before the first record is returned, the driver will terminate the connection, and Stata will report an execution-level failure.

Distinguishing Timeouts from Cancellations

Stata does not natively distinguish between network-level timeouts and database-side query cancellations. It surfaces whatever error the driver manager returns. To diagnose the cause in non-interactive mode, you must inspect the SQLSTATE and the error message:

• Network/Connection Timeout: Typically manifests with 08xxx SQLSTATE codes (e.g., 08S01 for communication link failure) or messages indicating the connection was reset by peer.
• Database-Side Timeout/Cancellation: Often returns specific statement-timeout codes (e.g., 57014 in PostgreSQL) or vendor-specific messages indicating the query exceeded a resource limit.

In non-interactive scripts, these errors will abort the do-file unless the command is wrapped in capture_. You can check the return code using:

capture odbc load mydata, "MyDSN", query("SELECT * FROM table")
if _rc != 0 {
    display "Query failed with code: " + string(_rc)"
}

Practical Mitigations for Long Queries

Since Stata cannot control the connection heartbeat directly via its commands, you must address the timeout at the environment level:

1. Modify DSN Settings: Increase the "Query Timeout" value in the ODBC Data Source Administrator or odbc.ini. Setting this to 0 often indicates no timeout.
2. Session-Level Commands: Use odbc exec to run database-specific commands before the load (e.g., "SET SESSION statement_timeout = 0;" for PostgreSQL).
3. Reduce Network Latency: Run the Stata instance on a host within the same local network as the database to prevent stateful firewalls or NAT devices from dropping "idle" TCP connections.
4. Batching: If the resultset is massive, consider using a loop with odbc load to fetch data in chunks using limit clauses, keeping the connection active frequently.

To provide more specific advice, are you using a specific database (e.g., SQL Server, PostgreSQL, MySQL) and is the failure occurring at a consistent interval of time?